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  • Which TCP ports to use?

    - by rowatt
    Is there a TCP port range which I can be sure will not be used by anything else for traffic between two machines? If I am reading RFC6335 correctly, I can be sure that no other applications will use specific ports in the Dynamic/Private/Ephemeral range of 49152-65535. However, if I understand correctly, it also states (section 8.1.2) that an application shouldn't assume that any given port in that range is available at any given time, which would mean I can't be 100% sure that it will be unused all the time. Specifically, I want to assign specific SSH traffic to a different port for the security benefit and so I can classify it differently for QoS purposes, and not have to worry about changing the port in the future.

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  • TCP handshake ok, then the client isn't receiving any packets from the server

    - by infgeoax
    Topology: Client ----- Intermediate Device ----- Server Client: win7 Intermediate Device: unknown Server: CentOS 5.8 The problem occurs when the client and server are trying to establish a SSL connection. It happens to one specific port, 2000. I haven't been able to replicate the problem with other port numbers. I captured packets on both client and server. After the TCP handshake, from the client's perspective, it's not receiving ACKs for its previously sent packets so it kept re-sending them. On the server side, however, it did receive those packets and sent ACK packets. The weird thing is, after the server sent those ACKs, it received a [RST, ACK] packet, from the intermediate device, for every packet it sent. What could be the cause?

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  • Relation between TCP/IP Keep Alive and HTTP Keep Alive timeout values

    - by Suresh Kumar
    I am trying to understand the relation between TCP/IP and HTTP timeout values. Are these two timeout values different or same? Most Web servers allow users to set the HTTP Keep Alive timeout value through some configuration. How is this value used by the Web servers? is this value just set on the underlying TCP/IP socket i.e is the HTTP Keep Alive timeout and TCP/IP Keep Alive Timeout same? or are they treated differently? My understanding is (maybe incorrect): The Web server uses the default timeout on the underlying TCP socket (i.e. indefinite) and creates Worker thread that counts down the specified HTTP timeout interval. When the Worker thread hits zero, it closes the connection.

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  • tcp connect hangs on SYN_SENT if something listens, gets CONN_REFUSED if nothing listens

    - by Amos Shapira
    I'm hitting a very strange problem - when I try to connect to one of our servers the client hangs with SYN_SENT if something listens on the port (e.g. Apache on port 80, sshd on port 22 or SMTP on port 25) but if I try to connect to a port on which nothing listens then I immediately get a "CONNECTION refused" error. Connecting to other applications (e.g. rsyncd on some arbitrary port) succeeds. I ran tcpdump on the server and see that the SYN packets arrive to it but it only sends a response if nothing listens on that port. e.g.: on the server I run: # tcpdump -nn port 81 06:49:34.641080 IP 10.x.y.z.49829 server.81: S 3966400723:3966400723(0) win 12320 06:49:34.641118 IP server.81 x.y.z.49829: R 0:0(0) ack 3966400724 win 0 But if I listen on this port, e.g. with nc -4lvvv 81 & Then the output of tcpdump is: 06:44:31.063614 IP x.y.z.45954 server.81: S 3493682313:3493682313(0) win 12320 (and repeats until I stop it) The server is CentOS 5, the client is Ubuntu 11.04, the connection is done between two LAN's over per-user TCP OpenVPN. Connection to other servers on that network do not have a problem. Connecting from the other servers on the same network to that server works fine. Connections from other clients in our office over openvpn is also not a problem. What am I missing? Thanks.

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  • Real benefits of tcp TIME-WAIT and implications in production environment

    - by user64204
    SOME THEORY I've been doing some reading on tcp TIME-WAIT (here and there) and what I read is that it's a value set to 2 x MSL (maximum segment life) which keeps a connection in the "connection table" for a while to guarantee that, "before your allowed to create a connection with the same tuple, all the packets belonging to previous incarnations of that tuple will be dead". Since segments received (apart from SYN under specific circumstances) while a connection is either in TIME-WAIT or no longer existing would be discarded, why not close the connection right away? Q1: Is it because there is less processing involved in dealing with segments from old connections and less processing to create a new connection on the same tuple when in TIME-WAIT (i.e. are there performance benefits)? If the above explanation doesn't stand, the only reason I see the TIME-WAIT being useful would be if a client sends a SYN for a connection before it sends remaining segments for an old connection on the same tuple in which case the receiver would re-open the connection but then get bad segments and and would have to terminate it. Q2: Is this analysis correct? Q3: Are there other benefits to using TIME-WAIT? SOME PRACTICE I've been looking at the munin graphs on a production server that I administrate. Here is one: As you can see there are more connections in TIME-WAIT than ESTABLISHED, around twice as many most of the time, on some occasions four times as many. Q4: Does this have an impact on performance? Q5: If so, is it wise/recommended to reduce the TIME-WAIT value (and what to)? Q6: Is this ratio of TIME-WAIT / ESTABLISHED connections normal? Could this be related to malicious connection attempts?

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  • Close TCP connection when owner process is already killed

    - by Otiel
    I have a Windows service that - when it starts - opens some WCF services to listen on the 8000 port. It happens that this service crashes sometimes. When it does, the TCP connection is not released, thus causing my service to throw an exception if I try to start it again: AddressAlreadyInUseException: There is already a listener on IP endpoint 0.0.0.0:8000 Some observations: When running CurrPorts or netstat -ano, I can see that the 8000 port is still in use (in LISTENING state) and is owned by the Process ID XXX that corresponded to my service process ID. But my service has already crashed, and does not appear in the Task Manager anymore. Thus I can't kill the process to free the port! Of course, running taskkill /PID XXX returns: ERROR: The process "XXX" not found. When running CurrPorts or netstat -b, I can see that the process name involved in creating the listening port is System, and not as MyService.exe (whereas it is MyService.exe when my service is running). I tried to use CurrPorts to close the connection, but I always get the following error message: Failed to close one or more TCP connections. Be aware that you must run this tool as admin in order to close TCP connections. (Useless to say, I do run CurrPorts as Administrator...) TCPView is not much help either: the process name associated to the 8000 port is <non-existent>, and doing "End process" or "Close connection" has no effect. I tried to see if there was not a child process associated with the PID XXX using Process Explorer, but no luck here. If I close my service properly (before it crashes), the TCP connection is correctly released. This is normal, as I close the WCF service hosts in the OnStop() event of my service. The only way I found to release the connection is to restart the server (which is not convenient in a production environment as you can guess). Waiting does not help, the TCP connection is never released. How can I close the connection without restarting the Windows server? PS: found some questions extremely similar to mine.

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  • TCP Server Memory management: #Connections Vs. #Requests

    - by Andrew
    Given that, there is no theoretical limit to number of concurrent TCP connections a Windows 2008 server can handle. Only thing will happen is, with each connection there will be memory consumption in server. Unfortunately, memory is not unlimited (and I want to utilize only physical memory). For example, lets say we've 2GB server memory. Now there are two extreme cases: Case 1: If we've allocated 64KB buffer for each connection (only to receive incoming request), then 32768 connections can consume all the 2GB of memory. This will not leave any memory to queue/process incoming requests from those connections. Case 2: On the other hand, lets say a single (or very few) connections continuously keeps sending request buffers (for example, video streaming from one connection to other) and server cannot process them within time, those buffers will get piled up in server and eventually will occupy most of the servers memory. And it will not leave any memory for new connection thereafter. This is the real dilemma in server design bugging me badly for last many days. If I can decide on max size of request buffer per connection and max number of requests to allow in queue per connection. Then, based on available server memory, it will then automatically set limit on max number of concurrent connections. How to decide on these limits to achieve best performance and throughput? I am just looking for perfect utilization of server resources. Are there any standard guidelines or empirical data available with someone who can share with me please.

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  • Can I reuse my existing TCP-Server?

    - by Helper Method
    At the moment I have an existing application which basically consists of a desktop GUI and a TCP server. The client connects to the server, and the server notifies the client if something interesting happens. Now I'm supposed to replace the desktop GUI by a web GUI, and I'm wondering if I have to rewrite the server to send http packets instead of tcp packets or if I can somehow use some sort of proxy to grab the tcp packets and forward them to the web client? Do I need some sort of comet server?

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  • TCP/UDP hole punching from and to the same NAT network

    - by Luc
    I was wondering if tcp/udp hole punching would still work when you are in the same network (behind a NAT), and what the packet's path would be. What happens when using hole punching on the same network, is that it will send a packet out with the same destination and source address. Only the source and destination port would differ. I imagine a router with NAT loopback enabled will handle this as it should, but how about other routers? Would they drop the packet, or would a router (the first?) from the ISP bounce the packet back after which it gets handled okay? I'm wondering because I was thinking about using this technique to circumvent a block between peers in a network (like a school network where clients can only access the internet, but any contact with each other is blocked). The only other option is to use a man in the middle as proxy (tunnel?). The disadvantage of this is that you have to have a server with significantly more bandwidth than one that would only do hole punching. Also the latency would increase significantly.

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  • Website latency and bad tcp packets

    - by Mistero Lupo
    I have multiple websites hosted on a Linode VPS and I'm having an issue with one of them: every page that I try to load has about 10 seconds latency. Apache logs are clean and the other websites on the same machine are running well. At a first glance I tought it was a memory problem since the VPS has got only 512M, but from the linode dashboard CPU and Disk I/O are normal. Anyway here we have the ram status: $ free -m total used free shared buffers cached Mem: 487 463 23 0 2 55 -/+ buffers/cache: 404 82 Swap: 255 155 100 Only 23M free, but if it was a memory problem why other websites are going as usual? I took a live capture with wireshark, and there are some duplicates SYN ACK packets just before the 10 seconds gap. I'm out of ideas, looking for some clues. Wireshark live capture screenshot As you can see from the image, the gap is after the last bad tcp. Thank you in advance. UPDATE I've checked Apache2 logs in debug error level, and this is where something is appening: 151.97.156.191 - - [14/Nov/2012:11:19:40 +0100] [www.fmaisi.it/sid#7f32c625a220][rid#7f32c6801578/subreq] (3) [perdir /home/fmaisi/sites/www.fmaisi.it/public_html/] applying pattern '^index\.php$' to uri 'index.php' 151.97.156.191 - - [14/Nov/2012:11:19:40 +0100] [www.fmaisi.it/sid#7f32c625a220][rid#7f32c6801578/subreq] (1) [perdir /home/fmaisi/sites/www.fmaisi.it/public_html/] pass through /home/fmaisi/sites/www.fmaisi.it/public_html/index.php 151.97.156.191 - - [14/Nov/2012:11:19:54 +0100] [www.fmaisi.it/sid#7f32c625a220][rid#7f32c6537c78/initial] (3) [perdir /home/fmaisi/sites/www.fmaisi.it/public_html/] strip per-dir prefix: /home/fmaisi/sites/www.fmaisi.it/public_html/wp-content/plugins/wp-filebase/wp-filebase_css.php -> wp-content/plugins/wp-filebase/wp-filebase_css.php 151.97.156.191 - - [14/Nov/2012:11:19:54 +0100] [www.fmaisi.it/sid#7f32c625a220][rid#7f32c6537c78/initial] (3) [perdir /home/fmaisi/sites/www.fmaisi.it/public_html/] applying pattern '^index\.php$' to uri 'wp-content/plugins/wp-filebase/wp-filebase_css.php' As you can see there is a gap of 14 seconds after the pass through of index.php. Any suggestions? I'm out of ideas again.

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  • Designing a persistent asynchronous TCP protocol

    - by dogglebones
    I have got a collection of web sites that need to send time-sensitive messages to host machines all over my metro area, each on its own generally dynamic IP. Until now, I have been doing this the way of the script kiddie: Each host machine runs an (s)FTP server, or an HTTP(s) server, and correspondingly has a certain port opened up by its gateway. Each host machine runs a program that watches a certain folder and automatically opens or prints or exec()s when a new file of a given extension shows up. Dynamic IP addresses are accommodated using a dynamic DNS service. Each web site does cURL or fsockopen or whatever and communicates directly with its recipient as-needed. This approach has been suprisingly reliable, however obvious issues have come up and the situation needs to be addressed. As stated, these messages are time-sensitive and failures need to be detected within minutes of submission by end-users. What I'm doing is building a messaging protocol. It will run on a machine and connection in my control. As far as the service is concerned, there is no distinction between web site and host machine -- there is only one device sending a message to another device. So that's where I'm at right now. I've got a skeleton server and a skeleton client. They can negotiate high-quality authentication and encryption. The (TCP) connection is persistent and asynchronous, and can handle delimited (i.e., read until \r\n or whatever) as well as length-prefixed (i.e., read exactly n bytes) messages. Unless somebody gives me a better idea, I think I'll handle messages as byte arrays. So I'm looking for suggestions on how to model the protocol itself -- at the application level. I'll mostly be transferring XML and DLM type files, as well as control messages for things like "handshake" and "is so-and-so online?" and so forth. Is there anything really stupid in my train of thought? Or anything I should read about before I get started? Stuff like that -- please and thanks.

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  • Strange 3-second tcp connection latencies (Linux, HTTP)

    - by user25417
    Our webservers with static content are experiencing strange 3 second latencies occasionally. Typically, an ApacheBench run ( 10000 requests, concurrency 1 or 40, no difference, but keepalive off) looks like this: Connection Times (ms) min mean[+/-sd] median max Connect: 2 10 152.8 3 3015 Processing: 2 8 34.7 3 663 Waiting: 2 8 34.7 3 663 Total: 4 19 157.2 6 3222 Percentage of the requests served within a certain time (ms) 50% 6 66% 7 75% 7 80% 7 90% 9 95% 11 98% 223 99% 225 100% 3222 (longest request) I have tried many things: - Apache2 2.2.9 with worker or prefork MPM, no difference (with KeepAliveTimeout 10-15) - Nginx 0.6.32 - various tcp parameters (net.core.somaxconn=3000, net.ipv4.tcp_sack=0, net.ipv4.tcp_dsack=0) - putting the files/DocumentRoot on tmpfs - shorewall on or off (i.e. empty iptables or not) - AllowOverride None is on for /, so no .htaccess checks (verified with strace) - the problem persists whether the webservers are accessed directly or through a Foundry load balancer Kernel is 2.6.32 (Debian Lenny backports), but it occurred with 2.6.26 also. IPv6 is enabled, but not used. Does the issue look familiar to anyone? Help/suggestions are much appreciated. It sounds a bit like a SYN,ACK packet getting lost or ignored.

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  • How to get at TCP RTT on Windows (Linux TCP_INFO) as an user

    - by FredAlkin
    I am porting a streaming TCP app from Linux to Windows. The app streams real-time audio data using a preexisting TCP protocol (so switching to UDP isn't an option). Further, I wish to avoid being "part of the problem" and requiring Administrator rights. The Linux code uses getsockopt(... ,SOL_TCP, TCP_INFO, ..) to get the RTT (round trip time) information from the TCP connection. The application level uses this to throttle the amount of data sent over the connection (apparently to balance quality with latency). Is there an equivalent to TCP_INFO on WIndows? (google tells me that Win2K and later supports "TCP Timestamps" which would provide this information, but I've yet to find a way to get at it. Thanks in advance.

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  • [Java] Listening for TCP and UDP requests on the same port

    - by user339328
    I am writing a Client/Server set of programs Depending on the operation requested by the client, I use make TCP or UDP request. Implementing the client side is straight-forward, since I can easily open connection with any protocol and send the request to the server-side. On the servers-side, on the other hand, I would like to listen both for UDP and TCP connections on the same port. Moreover, I like the the server to open new thread for each connection request. I have adopted the approach explained in: link text I have extended this code sample by creating new threads for each TCP/UDP request. This works correctly if I use TCP only, but it fails when I attempt to make UDP bindings. Please give me any suggestion how can I correct this. tnx

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  • NFS Mounts Issues

    - by user554005
    Having some issue with a NFS Setup on the clients it just times out refuses to connect [root@host9 ~]# mount 192.168.0.17:/home/export /mnt/export mount: mount to NFS server '192.168.0.17' failed: timed out (retrying). mount: mount to NFS server '192.168.0.17' failed: timed out (retrying). mount: mount to NFS server '192.168.0.17' failed: timed out (retrying). mount: mount to NFS server '192.168.0.17' failed: timed out (retrying). Here are the settings I'm using: [root@host17 /home/export]# cat /etc/hosts.allow # # hosts.allow This file contains access rules which are used to # allow or deny connections to network services that # either use the tcp_wrappers library or that have been # started through a tcp_wrappers-enabled xinetd. # # See 'man 5 hosts_options' and 'man 5 hosts_access' # for information on rule syntax. # See 'man tcpd' for information on tcp_wrappers # portmap: 192.168.0.0/255.255.255.0 lockd: 192.168.0.0/255.255.255.0 rquotad: 192.168.0.0/255.255.255.0 mountd: 192.168.0.0/255.255.255.0 statd: 192.168.0.0/255.255.255.0 [root@host17 /home/export]# cat /etc/hosts.deny # # hosts.deny This file contains access rules which are used to # deny connections to network services that either use # the tcp_wrappers library or that have been # started through a tcp_wrappers-enabled xinetd. # # The rules in this file can also be set up in # /etc/hosts.allow with a 'deny' option instead. # # See 'man 5 hosts_options' and 'man 5 hosts_access' # for information on rule syntax. # See 'man tcpd' for information on tcp_wrappers # portmap:ALL lockd:ALL mountd:ALL rquotad:ALL statd:ALL [root@host17 /home/export]# cat /etc/exports /home/export 192.168.0.0/255.255.255.0(rw) [root@host17 /home/export]# iptables -L Chain INPUT (policy ACCEPT) target prot opt source destination RH-Firewall-1-INPUT all -- anywhere anywhere Chain FORWARD (policy ACCEPT) target prot opt source destination RH-Firewall-1-INPUT all -- anywhere anywhere Chain OUTPUT (policy ACCEPT) target prot opt source destination Chain RH-Firewall-1-INPUT (2 references) target prot opt source destination ACCEPT all -- anywhere anywhere ACCEPT icmp -- anywhere anywhere icmp any ACCEPT esp -- anywhere anywhere ACCEPT ah -- anywhere anywhere ACCEPT udp -- anywhere 224.0.0.251 udp dpt:mdns ACCEPT udp -- anywhere anywhere udp dpt:ipp ACCEPT tcp -- anywhere anywhere tcp dpt:ipp ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:ssh ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:http ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:https ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:6379 ACCEPT udp -- 192.168.0.0/24 anywhere state NEW udp dpt:sunrpc ACCEPT tcp -- 192.168.0.0/24 anywhere state NEW tcp dpt:sunrpc ACCEPT tcp -- 192.168.0.0/24 anywhere state NEW tcp dpt:nfs ACCEPT tcp -- 192.168.0.0/24 anywhere state NEW tcp dpt:32803 ACCEPT udp -- 192.168.0.0/24 anywhere state NEW udp dpt:filenet-rpc ACCEPT tcp -- 192.168.0.0/24 anywhere state NEW tcp dpt:892 ACCEPT udp -- 192.168.0.0/24 anywhere state NEW udp dpt:892 ACCEPT tcp -- 192.168.0.0/24 anywhere state NEW tcp dpt:rquotad ACCEPT udp -- 192.168.0.0/24 anywhere state NEW udp dpt:rquotad ACCEPT tcp -- 192.168.0.0/24 anywhere state NEW tcp dpt:pftp ACCEPT udp -- 192.168.0.0/24 anywhere state NEW udp dpt:pftp REJECT all -- anywhere anywhere reject-with icmp-host-prohibited on the clients here is some rpcinfos [root@host9 ~]# rpcinfo -p 192.168.0.17 program vers proto port 100000 4 tcp 111 portmapper 100000 3 tcp 111 portmapper 100000 2 tcp 111 portmapper 100000 4 udp 111 portmapper 100000 3 udp 111 portmapper 100000 2 udp 111 portmapper 100011 1 udp 875 rquotad 100011 2 udp 875 rquotad 100011 1 tcp 875 rquotad 100011 2 tcp 875 rquotad 100005 1 udp 45857 mountd 100005 1 tcp 55772 mountd 100005 2 udp 34021 mountd 100005 2 tcp 59542 mountd 100005 3 udp 60930 mountd 100005 3 tcp 53086 mountd 100003 2 udp 2049 nfs 100003 3 udp 2049 nfs 100003 4 udp 2049 nfs 100227 2 udp 2049 nfs_acl 100227 3 udp 2049 nfs_acl 100003 2 tcp 2049 nfs 100003 3 tcp 2049 nfs 100003 4 tcp 2049 nfs 100227 2 tcp 2049 nfs_acl 100227 3 tcp 2049 nfs_acl 100021 1 udp 59832 nlockmgr 100021 3 udp 59832 nlockmgr 100021 4 udp 59832 nlockmgr 100021 1 tcp 36140 nlockmgr 100021 3 tcp 36140 nlockmgr 100021 4 tcp 36140 nlockmgr 100024 1 udp 46494 status 100024 1 tcp 49672 status [root@host9 ~]# [root@host9 ~]# rpcinfo -u 192.168.0.17 nfs rpcinfo: RPC: Timed out program 100003 version 0 is not available [root@host9 ~]# rpcinfo -u 192.168.0.17 portmap program 100000 version 2 ready and waiting program 100000 version 3 ready and waiting program 100000 version 4 ready and waiting [root@host9 ~]# rpcinfo -u 192.168.0.17 mount rpcinfo: RPC: Timed out program 100005 version 0 is not available [root@host9 ~]# I'm running CentOS 5.8 on all systems

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  • TCP stops sending weirdly.

    - by Utoah
    In case to find out the cause of TCP retransmits on my Linux (RHEL, kernel 2.6.18) servers connecting to the same switch. I had a client-server pair send "Hello" to each other every 200us and captured the packets with tcpdump on the client machine. The command I used to mimic client and server are: while [ 0 ]; do echo "Hello"; usleep 200; done | nc server 18510 while [ 0 ]; do echo "Hello"; usleep 200; done | nc -l 18510 When the server machine was busy serving some other requests, the client suffered from abrupt retransmits occasionally. But the output of tcpdump seemed irrational. 16:04:58.898970 IP server.18510 > client.34533: P 4531:4537(6) ack 3204 win 123 <nop,nop,timestamp 1923778643 3452833828> 16:04:58.901797 IP client.34533 > server.18510: P 3204:3210(6) ack 4537 win 33 <nop,nop,timestamp 3452833831 1923778643> 16:04:58.901855 IP server.18510 > client.34533: P 4537:4549(12) ack 3210 win 123 <nop,nop,timestamp 1923778646 3452833831> 16:04:58.903871 IP client.34533 > server.18510: P 3210:3216(6) ack 4549 win 33 <nop,nop,timestamp 3452833833 1923778646> 16:04:58.903950 IP server.18510 > client.34533: P 4549:4555(6) ack 3216 win 123 <nop,nop,timestamp 1923778648 3452833833> 16:04:58.905796 IP client.34533 > server.18510: P 3216:3222(6) ack 4555 win 33 <nop,nop,timestamp 3452833835 1923778648> 16:04:58.905860 IP server.18510 > client.34533: P 4555:4561(6) ack 3222 win 123 <nop,nop,timestamp 1923778650 3452833835> 16:04:58.908903 IP client.34533 > server.18510: P 3222:3228(6) ack 4561 win 33 <nop,nop,timestamp 3452833838 1923778650> 16:04:58.908966 IP server.18510 > client.34533: P 4561:4567(6) ack 3228 win 123 <nop,nop,timestamp 1923778653 3452833838> 16:04:58.911855 IP client.34533 > server.18510: P 3228:3234(6) ack 4567 win 33 <nop,nop,timestamp 3452833841 1923778653> 16:04:59.112573 IP client.34533 > server.18510: P 3228:3234(6) ack 4567 win 33 <nop,nop,timestamp 3452834042 1923778653> 16:04:59.112648 IP server.18510 > client.34533: P 4567:5161(594) ack 3234 win 123 <nop,nop,timestamp 1923778857 3452834042> 16:04:59.112659 IP client.34533 > server.18510: P 3234:3672(438) ack 5161 win 35 <nop,nop,timestamp 3452834042 1923778857> 16:04:59.114427 IP server.18510 > client.34533: P 5161:5167(6) ack 3672 win 126 <nop,nop,timestamp 1923778858 3452834042> 16:04:59.114439 IP client.34533 > server.18510: P 3672:3678(6) ack 5167 win 35 <nop,nop,timestamp 3452834044 1923778858> 16:04:59.116435 IP server.18510 > client.34533: P 5167:5173(6) ack 3678 win 126 <nop,nop,timestamp 1923778860 3452834044> 16:04:59.116444 IP client.34533 > server.18510: P 3678:3684(6) ack 5173 win 35 <nop,nop,timestamp 3452834046 1923778860> Packet 3228:3234(6) from client was retransmitted due to ack timeout. What I could not understand was that the client machine did not send out any packets after the first 3228:3234(6) packets was sent. The server machine had advertised a window (scaled) large enough. The data transfer up to the retransmit was fine which meant no slow start should be in action. What can cause the client machine to stop sending until the packet timed out? BTW, I am unable to run tcpdump on the server machine.

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  • Cisco 881 losing NAT NVI translation config after reload

    - by MasterRoot24
    This is a weird one, so I'll try to explain in as much detail as I can so I'm giving the whole picture. As I've mentioned in my other questions, I'm in the process of setting up a new Cisco 881 as my WAN router and NAT firewall. I'm facing an issue where NAT NVI rules that I have configured are not enabled after a reload of the router, regardless of the fact that they are present in the startup-config. In order to clarify this a little, here's the relevant section of my current running-config: Router1#show running-config | include nat source ip nat source list 1 interface FastEthernet4 overload ip nat source list 2 interface FastEthernet4 overload ip nat source static tcp 192.168.1.x 1723 interface FastEthernet4 1723 ip nat source static tcp 192.168.1.x 80 interface FastEthernet4 80 ip nat source static tcp 192.168.1.x 443 interface FastEthernet4 443 ip nat source static tcp 192.168.1.x 25 interface FastEthernet4 25 ip nat source static tcp 192.168.1.x 587 interface FastEthernet4 587 ip nat source static tcp 192.168.1.x 143 interface FastEthernet4 143 ip nat source static tcp 192.168.1.x 993 interface FastEthernet4 993 ...and here's the mappings 'in action': Router1#show ip nat nvi translations | include --- tcp <WAN IP>:25 192.168.1.x:25 --- --- tcp <WAN IP>:80 192.168.1.x:80 --- --- tcp <WAN IP>:143 192.168.1.x:143 --- --- tcp <WAN IP>:443 192.168.1.x:443 --- --- tcp <WAN IP>:587 192.168.1.x:587 --- --- tcp <WAN IP>:993 192.168.1.x:993 --- --- tcp <WAN IP>:1723 192.168.1.x:1723 --- --- ...and here's proof that the mappings are saved to startup-config: Router1#show startup-config | include nat source ip nat source list 1 interface FastEthernet4 overload ip nat source list 2 interface FastEthernet4 overload ip nat source static tcp 192.168.1.x 1723 interface FastEthernet4 1723 ip nat source static tcp 192.168.1.x 80 interface FastEthernet4 80 ip nat source static tcp 192.168.1.x 443 interface FastEthernet4 443 ip nat source static tcp 192.168.1.x 25 interface FastEthernet4 25 ip nat source static tcp 192.168.1.x 587 interface FastEthernet4 587 ip nat source static tcp 192.168.1.x 143 interface FastEthernet4 143 ip nat source static tcp 192.168.1.x 993 interface FastEthernet4 993 However, look what happens after a reload of the router: Router1#reload Proceed with reload? [confirm]Connection to router closed by remote host. Connection to router closed. $ ssh joe@router Password: Authorized Access only Router1>en Password: Router1#show ip nat nvi translations | include --- Router1# Router1#show ip nat translations | include --- tcp 188.222.181.173:25 192.168.1.2:25 --- --- tcp 188.222.181.173:80 192.168.1.2:80 --- --- tcp 188.222.181.173:143 192.168.1.2:143 --- --- tcp 188.222.181.173:443 192.168.1.2:443 --- --- tcp 188.222.181.173:587 192.168.1.2:587 --- --- tcp 188.222.181.173:993 192.168.1.2:993 --- --- tcp 188.222.181.173:1723 192.168.1.2:1723 --- --- Router1# Here's proof that the running config should have the mappings setup as NVI: Router1#show running-config | include nat source ip nat source list 1 interface FastEthernet4 overload ip nat source list 2 interface FastEthernet4 overload ip nat source static tcp 192.168.1.2 1723 interface FastEthernet4 1723 ip nat source static tcp 192.168.1.2 80 interface FastEthernet4 80 ip nat source static tcp 192.168.1.2 443 interface FastEthernet4 443 ip nat source static tcp 192.168.1.2 25 interface FastEthernet4 25 ip nat source static tcp 192.168.1.2 587 interface FastEthernet4 587 ip nat source static tcp 192.168.1.2 143 interface FastEthernet4 143 ip nat source static tcp 192.168.1.2 993 interface FastEthernet4 993 At this point, the mappings are not working (inbound connections from WAN on the HTTP/IMAP fail). I presume that this is because my interfaces are using ip nat enable for use with NVI mappings, instead of ip nat inside/outside. So, I re-apply the mappings: Router1#configure ter Router1#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router1(config)#ip nat source static tcp 192.168.1.2 1723 interface FastEthernet4 1723 Router1(config)#ip nat source static tcp 192.168.1.2 80 interface FastEthernet4 80 Router1(config)#ip nat source static tcp 192.168.1.2 443 interface FastEthernet4 443 Router1(config)#ip nat source static tcp 192.168.1.2 25 interface FastEthernet4 25 Router1(config)#ip nat source static tcp 192.168.1.2 587 interface FastEthernet4 587 Router1(config)#ip nat source static tcp 192.168.1.2 143 interface FastEthernet4 143 Router1(config)#ip nat source static tcp 192.168.1.2 993 interface FastEthernet4 993 Router1(config)#end ... then they show up correctly: Router1#show ip nat nvi translations | include --- tcp 188.222.181.173:25 192.168.1.2:25 --- --- tcp 188.222.181.173:80 192.168.1.2:80 --- --- tcp 188.222.181.173:143 192.168.1.2:143 --- --- tcp 188.222.181.173:443 192.168.1.2:443 --- --- tcp 188.222.181.173:587 192.168.1.2:587 --- --- tcp 188.222.181.173:993 192.168.1.2:993 --- --- tcp 188.222.181.173:1723 192.168.1.2:1723 --- --- Router1# Router1#show ip nat translations | include --- Router1# ... furthermore, now from both WAN and LAN, the services mapped above now work until the next reload. All of the above is required every time I have to reload the router (which is all too often at the moment :-( ). Here's my full current config: ! ! Last configuration change at 20:20:15 UTC Tue Dec 11 2012 by xxx version 15.2 no service pad service timestamps debug datetime msec service timestamps log datetime msec service password-encryption ! hostname xxx ! boot-start-marker boot-end-marker ! ! enable secret 4 xxxx ! aaa new-model ! ! aaa authentication login local_auth local ! ! ! ! ! aaa session-id common ! memory-size iomem 10 ! crypto pki trustpoint TP-self-signed-xxx enrollment selfsigned subject-name cn=IOS-Self-Signed-Certificate-xxx revocation-check none rsakeypair TP-self-signed-xxx ! ! crypto pki certificate chain TP-self-signed-xxx certificate self-signed 01 xxx quit ip gratuitous-arps ip auth-proxy max-login-attempts 5 ip admission max-login-attempts 5 ! ! ! ! ! ip domain list dmz.xxx.local ip domain list xxx.local ip domain name dmz.xxx.local ip name-server 192.168.1.x ip cef login block-for 3 attempts 3 within 3 no ipv6 cef ! ! multilink bundle-name authenticated license udi pid CISCO881-SEC-K9 sn xxx ! ! username admin privilege 15 secret 4 xxx username joe secret 4 xxx ! ! ! ! ! ip ssh time-out 60 ! ! ! ! ! ! ! ! ! interface FastEthernet0 no ip address ! interface FastEthernet1 no ip address ! interface FastEthernet2 no ip address ! interface FastEthernet3 switchport access vlan 2 no ip address ! interface FastEthernet4 ip address dhcp ip access-group 101 in ip nat enable duplex auto speed auto ! interface Vlan1 ip address 192.168.1.x 255.255.255.0 no ip redirects no ip unreachables no ip proxy-arp ip nat enable ! interface Vlan2 ip address 192.168.0.x 255.255.255.0 ! ip forward-protocol nd ip http server ip http access-class 1 ip http authentication local ip http secure-server ! ! ip nat source list 1 interface FastEthernet4 overload ip nat source list 2 interface FastEthernet4 overload ip nat source static tcp 192.168.1.x 1723 interface FastEthernet4 1723 ! ! access-list 1 permit 192.168.0.0 0.0.0.255 access-list 2 permit 192.168.1.0 0.0.0.255 access-list 101 permit udp 193.x.x.0 0.0.0.255 any eq 5060 access-list 101 deny udp any any eq 5060 access-list 101 permit ip any any ! ! ! ! control-plane ! ! banner motd Authorized Access only ! line con 0 exec-timeout 15 0 login authentication local_auth line aux 0 exec-timeout 15 0 login authentication local_auth line vty 0 4 access-class 2 in login authentication local_auth length 0 transport input all ! ! end I'd appreciate it greatly if anyone can help me find out why these mappings are not setup correctly using the saved config after a reload.

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  • Help me solve my problem with NPR Media Player

    - by Calcipher
    First of, let me apologize for this getting a bit technical. Several weeks ago, I found that while using NPR's media player (e.g. click on 'Listen to the Show' - this is what I've been using as a test) the stream would suddenly halt after a minute or three. I could not get the stream to restart without reloading the page. Now, I assumed this was an issue with NPR's player and Linux (or just a bug in their stuff in general) so I began to dig, the following is what I have tried to date (please note, the tldr; option is to skip to the latest thing as I think I know what is causing the problem). Note: All testing has been done, for consistency purposes, on a clean install of Chromium with no pluggins running. My machine is Ubuntu 10.10x64. First thing I always try, I disabled all firewall stuff on the system (UFW, default deny all, allow ssh). No change, firewall back up for all additional tests unless otherwise noted. In any case, UFW is stateful, so connections it started on a non-specified on different ports will continue to work. I deleted my ~/.macromeda and ~/.adobe folders, restarted (just to be sure) and tried. Program still froze. I decided the problem might be with my install of flash, so I purged the version I had (and the home folders again). I installed the x64 version of flash from a PPA. This had no effect. I decided that the problem might be with the version of flash, so I purged the x64 version and installed the standard x32 version that comes with Ubuntu. No luck. Back to the x64 version for consistency, I decided to set up a 64-bit mini 'clone' of my system in VirtualBox. I was able to run the media player with no problem. I rsynced (in archive mode) my home directory from my real machine to the virtual machine (with bridged networking, so it was fully visible on the network). I also used a few tricks to install ALL of the same software (and repositories) from the real machine to the virtual machine. I was still able to listen to the player. I decided that the problem was with my install (after all, it had gone through two major version upgrades). As I have /home/ on a separate partition it was easy to reinstall and use the same trick from #6 to have my system up and running again within about an hour. I continue to have issues with the NPR Media Player. By this point the weekend had come. At work, I use a wired connection while at home I use a wireless connection. For some reason I forgot that I was having problems and used the NPR Media Player over the weekend. Low and behold it worked just fine at home on wireless (note: for various reasons, I could not test this on wired at home). Following from #6, I decided that the problem was either something with the network at work or still something with my account. As the latter was easier to test, I created a new account on my system and used that at work. The Media Player worked. At a loss, I decided to watch the traffic with tshark (the text based brother of wireshark) - X's to protect the innocent, I am the XXX.24.200.XXX: sudo tshark -i eth0 -p -t a -R "ip.addr == XXX.24.200.XXX && ip.addr == XXX.166.98.XXX" As you would expect, there were tons and tons of packets, but each and every time the player froze, this is what I got 08:42:20.679200 XXX.166.98.XXX - XXX.24.200.XXX TCP macromedia-fcs 56371 [PSH, ACK] Seq=817686 Ack=6 Win=65535 Len=1448 TSV=495713325 TSER=396467 08:42:20.718602 XXX.24.200.XXX - XXX.166.98.XXX TCP [TCP ZeroWindow] 56371 macromedia-fcs [ACK] Seq=6 Ack=819134 Win=0 Len=0 TSV=396475 TSER=495713325 08:42:21.050183 XXX.166.98.XXX - XXX.24.200.XXX TCP [TCP ZeroWindowProbe] macromedia-fcs 56371 [ACK] Seq=819134 Ack=6 Win=65535 Len=1 TSV=495713362 TSER=396475 08:42:21.050221 XXX.24.200.XXX - XXX.166.98.XXX TCP [TCP ZeroWindowProbeAck] [TCP ZeroWindow] 56371 macromedia-fcs [ACK] Seq=6 Ack=819134 Win=0 Len=0 TSV=396508 TSER=495713362 08:42:21.680548 XXX.166.98.XXX - XXX.24.200.XXX TCP [TCP ZeroWindowProbe] macromedia-fcs 56371 [ACK] Seq=819134 Ack=6 Win=65535 Len=1 TSV=495713425 TSER=396508 08:42:21.680605 XXX.24.200.XXX - XXX.166.98.XXX TCP [TCP ZeroWindowProbeAck] [TCP ZeroWindow] 56371 macromedia-fcs [ACK] Seq=6 Ack=819134 Win=0 Len=0 TSV=396571 TSER=495713425 08:42:22.910354 XXX.166.98.XXX - XXX.24.200.XXX TCP [TCP ZeroWindowProbe] macromedia-fcs 56371 [ACK] Seq=819134 Ack=6 Win=65535 Len=1 TSV=495713548 TSER=396571 08:42:22.910400 XXX.24.200.XXX - XXX.166.98.XXX TCP [TCP ZeroWindowProbeAck] [TCP ZeroWindow] 56371 macromedia-fcs [ACK] Seq=6 Ack=819134 Win=0 Len=0 TSV=396694 TSER=495713548 08:42:25.340458 XXX.166.98.XXX - XXX.24.200.XXX TCP [TCP ZeroWindowProbe] macromedia-fcs 56371 [ACK] Seq=819134 Ack=6 Win=65535 Len=1 TSV=495713791 TSER=396694 08:42:25.340517 XXX.24.200.XXX - XXX.166.98.XXX TCP [TCP ZeroWindowProbeAck] [TCP ZeroWindow] 56371 macromedia-fcs [ACK] Seq=6 Ack=819134 Win=0 Len=0 TSV=396937 TSER=495713791 08:42:30.170698 XXX.166.98.XXX - XXX.24.200.XXX TCP [TCP ZeroWindowProbe] macromedia-fcs 56371 [ACK] Seq=819134 Ack=6 Win=65535 Len=1 TSV=495714274 TSER=396937 08:42:30.170746 XXX.24.200.XXX - XXX.166.98.XXX TCP [TCP ZeroWindowProbeAck] [TCP ZeroWindow] 56371 macromedia-fcs [ACK] Seq=6 Ack=819134 Win=0 Len=0 TSV=397420 TSER=495714274 08:42:39.801738 XXX.166.98.XXX - XXX.24.200.XXX TCP [TCP ZeroWindowProbe] macromedia-fcs 56371 [ACK] Seq=819134 Ack=6 Win=65535 Len=1 TSV=495715237 TSER=397420 08:42:39.801784 XXX.24.200.XXX - XXX.166.98.XXX TCP [TCP ZeroWindowProbeAck] [TCP ZeroWindow] 56371 macromedia-fcs [ACK] Seq=6 Ack=819134 Win=0 Len=0 TSV=398383 TSER=495715237 08:42:59.032648 XXX.166.98.XXX - XXX.24.200.XXX TCP [TCP ZeroWindowProbe] macromedia-fcs 56371 [ACK] Seq=819134 Ack=6 Win=65535 Len=1 TSV=495717160 TSER=398383 08:42:59.032696 XXX.24.200.XXX - XXX.166.98.XXX TCP [TCP ZeroWindowProbeAck] [TCP ZeroWindow] 56371 macromedia-fcs [ACK] Seq=6 Ack=819134 Win=0 Len=0 TSV=400306 TSER=495717160 08:43:00.267721 XXX.24.200.XXX - XXX.166.98.XXX TCP 56371 macromedia-fcs [FIN, ACK] Seq=6 Ack=819134 Win=0 Len=0 TSV=400430 TSER=495717160 08:43:00.267827 XXX.24.200.XXX - XXX.166.98.XXX TCP 56371 macromedia-fcs [RST, ACK] Seq=7 Ack=819134 Win=65535 Len=0 TSV=400430 TSER=495717160 So, as you can see, my machine is sending out a ZeroWindow packet (which I think means some buffer or another filled up) which causes the Media Player to halt (unfortunately, terminally - no controls on it really do anything anymore). Any ideas, at all, what would cause this? Why only on eth0 under my main account?

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  • Java, server client TCP communication ends with RST

    - by Senne
    I'm trying to figure out if this is normal. Because without errors, a connection should be terminated by: FIN -> <- ACK <- FIN ACK -> I get this at the end of a TCP connection (over SSL, but i also get it with non-encrypted): From To 1494 server client TCP search-agent > 59185 [PSH, ACK] Seq=25974 Ack=49460 Win=63784 Len=50 1495 client server TCP 59185 > search-agent [ACK] Seq=49460 Ack=26024 Win=63565 Len=0 1496 client server TCP 59185 > search-agent [PSH, ACK] Seq=49460 Ack=26024 Win=63565 Len=23 1497 client server TCP 59185 > search-agent [FIN, ACK] Seq=49483 Ack=26024 Win=63565 Len=0 1498 server client TCP search-agent > 59185 [PSH, ACK] Seq=26024 Ack=49484 Win=63784 Len=23 1499 client server TCP 59185 > search-agent [RST, ACK] Seq=49484 Ack=26047 Win=0 Len=0 The client exits normally and reaches socket.close, shouldn't then the connection be shut down normally, without a reset? I can't find anything about the TCP streams of java on google... Here is my code: Server: package Security; import java.io.*; import java.net.*; import javax.net.ServerSocketFactory; import javax.net.ssl.*; import java.util.*; public class SSLDemoServer { private static ServerSocket serverSocket; private static final int PORT = 1234; public static void main(String[] args) throws IOException { int received = 0; String returned; ObjectInputStream input = null; PrintWriter output = null; Socket client; System.setProperty("javax.net.ssl.keyStore", "key.keystore"); System.setProperty("javax.net.ssl.keyStorePassword", "vwpolo"); System.setProperty("javax.net.ssl.trustStore", "key.keystore"); System.setProperty("javax.net.ssl.trustStorePassword", "vwpolo"); try { System.out.println("Trying to set up server ..."); ServerSocketFactory factory = SSLServerSocketFactory.getDefault(); serverSocket = factory.createServerSocket(PORT); System.out.println("Server started!\n"); } catch (IOException ioEx) { System.out.println("Unable to set up port!"); ioEx.printStackTrace(); System.exit(1); } while(true) { client = serverSocket.accept(); System.out.println("Client trying to connect..."); try { System.out.println("Trying to create inputstream..."); input = new ObjectInputStream(client.getInputStream()); System.out.println("Trying to create outputstream..."); output = new PrintWriter(client.getOutputStream(), true); System.out.println("Client successfully connected!"); while( true ) { received = input.readInt(); returned = Integer.toHexString(received); System.out.print(" " + received); output.println(returned.toUpperCase()); } } catch(SSLException sslEx) { System.out.println("Connection failed! (non-SSL connection?)\n"); client.close(); continue; } catch(EOFException eofEx) { System.out.println("\nEnd of client data.\n"); } catch(IOException ioEx) { System.out.println("I/O problem! (correct inputstream?)"); } try { input.close(); output.close(); } catch (Exception e) { } client.close(); System.out.println("Client closed.\n"); } } } Client: package Security; import java.io.*; import java.net.*; import javax.net.ssl.*; import java.util.*; public class SSLDemoClient { private static InetAddress host; private static final int PORT = 1234; public static void main(String[] args) { System.setProperty("javax.net.ssl.keyStore", "key.keystore"); System.setProperty("javax.net.ssl.keyStorePassword", "vwpolo"); System.setProperty("javax.net.ssl.trustStore", "key.keystore"); System.setProperty("javax.net.ssl.trustStorePassword", "vwpolo"); System.out.println("\nCreating SSL socket ..."); SSLSocket socket = null; try { host = InetAddress.getByName("192.168.56.101"); SSLSocketFactory factory = (SSLSocketFactory) SSLSocketFactory.getDefault(); socket = (SSLSocket) factory.createSocket(host, PORT); socket.startHandshake(); } catch(UnknownHostException uhEx) { System.out.println("\nHost ID not found!\n"); System.exit(1); } catch(SSLException sslEx) { System.out.println("\nHandshaking unsuccessful ..."); System.exit(1); } catch (IOException e) { e.printStackTrace(); } System.out.println("\nHandshaking succeeded ...\n"); SSLClientThread client = new SSLClientThread(socket); SSLReceiverThread receiver = new SSLReceiverThread(socket); client.start(); receiver.start(); try { client.join(); receiver.join(); System.out.println("Trying to close..."); socket.close(); } catch(InterruptedException iEx) { iEx.printStackTrace(); } catch(IOException ioEx) { ioEx.printStackTrace(); } System.out.println("\nClient finished."); } } class SSLClientThread extends Thread { private SSLSocket socket; public SSLClientThread(SSLSocket s) { socket = s; } public void run() { try { ObjectOutputStream output = new ObjectOutputStream(socket.getOutputStream()); for( int i = 1; i < 1025; i++) { output.writeInt(i); sleep(10); output.flush(); } output.flush(); sleep(1000); output.close(); } catch(IOException ioEx) { System.out.println("Socket closed or unable to open socket."); } catch(InterruptedException iEx) { iEx.printStackTrace(); } } } class SSLReceiverThread extends Thread { private SSLSocket socket; public SSLReceiverThread(SSLSocket s) { socket = s; } public void run() { String response = null; BufferedReader input = null; try { input = new BufferedReader( new InputStreamReader(socket.getInputStream())); try { response = input.readLine(); while(!response.equals(null)) { System.out.print(response + " "); response = input.readLine(); } } catch(Exception e) { System.out.println("\nEnd of server data.\n"); } input.close(); } catch(IOException ioEx) { ioEx.printStackTrace(); } } }

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  • Iptables working strangely

    - by user109985
    I have Ubuntu 12.04 x64 installed in my laptop. I'm quite new to linux, and I wanted to specify certain rules for the iptables firewall. This is the saved config of my iptables: *mangle :PREROUTING ACCEPT [0:0] :INPUT ACCEPT [0:0] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [0:0] :POSTROUTING ACCEPT [0:0] COMMIT *nat :PREROUTING ACCEPT [0:0] :INPUT ACCEPT [0:0] :OUTPUT ACCEPT [0:0] :POSTROUTING ACCEPT [0:0] -A PREROUTING -p tcp -m tcp --dport 3306 -j DNAT --to-destination 192.168.1.100:3306 -A PREROUTING -p tcp -m tcp --dport 11002 -j DNAT --to-destination 192.168.1.100:11002 -A PREROUTING -p tcp -m tcp --dport 13000 -j DNAT --to-destination 192.168.1.100:13000 -A PREROUTING -p tcp -m tcp --dport 13001 -j DNAT --to-destination 192.168.1.100:13001 -A PREROUTING -p tcp -m tcp --dport 13002 -j DNAT --to-destination 192.168.1.100:13002 -A PREROUTING -p tcp -m tcp --dport 13003 -j DNAT --to-destination 192.168.1.100:13003 -A PREROUTING -p tcp -m tcp --dport 13004 -j DNAT --to-destination 192.168.1.100:13004 -A PREROUTING -p tcp -m tcp --dport 13061 -j DNAT --to-destination 192.168.1.100:13061 -A PREROUTING -p tcp -m tcp --dport 13099 -j DNAT --to-destination 192.168.1.100:13099 -A POSTROUTING -j MASQUERADE COMMIT *filter :INPUT DROP [0:0] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [0:0] -A INPUT -i eth0 -p tcp -m tcp --dport 3306 -j ACCEPT -A INPUT -i eth0 -p tcp -m tcp --dport 80 -j ACCEPT COMMIT In theory, what it does is to drop all connections in all ports except for http, mysql and few other ports. Moreover, it redirects all mysql and 13000-13004..etc port connections to a specific local ip in the same port, which is 192.168.1.100. But what I find strange is that when my firewall is active, it blocks absolutely all the input connections, even those which must not block (http, mysql). In fact, I'm literally blocked and I can't establish any external connection. What am I doing wrong? PS: I tested the firewall without those redirections, and it still block all inputs, so I suppose it's not the problem.

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  • WCF Duplex net.tcp issues on win7

    - by Tom
    We have a WCF service with multiple clients to schedule operations amongst clients. It worked great on XP. Moving to win7, I can only connect a client to the server on the same machine. At this point, I'm thinking it's something to do with IPv6, but I'm stumped as to how to proceed. Client trying to connect to a remote server gives the following exception: System.ServiceModel.EndpointNotFoundException: Could not connect to net.tcp://10.7.11.14:18297/zetec/Service/SchedulerService/Scheduler. The connection attempt lasted for a time span of 00:00:21.0042014. TCP error code 10060: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond 10.7.11.14:18297. --- System.Net.Sockets.SocketException: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond 10.7.11.14:18297 The service is configured like so: <system.serviceModel> <services> <service name="SchedulerService" behaviorConfiguration="SchedulerServiceBehavior"> <host> <baseAddresses> <add baseAddress="net.tcp://localhost/zetec/Service/SchedulerService"/> </baseAddresses> </host> <endpoint address="net.tcp://localhost:18297/zetec/Service/SchedulerService/Scheduler" binding="netTcpBinding" bindingConfiguration = "ConfigBindingNetTcp" contract="IScheduler" /> <endpoint address="net.tcp://localhost:18297/zetec/Service/SchedulerService/Scheduler" binding="netTcpBinding" bindingConfiguration = "ConfigBindingNetTcp" contract="IProcessingNodeControl" /> </service> </services> <bindings> <netTcpBinding> <binding name = "ConfigBindingNetTcp" portSharingEnabled="True"> <security mode="None"/> </binding> </netTcpBinding > </bindings> <behaviors> <serviceBehaviors> <behavior name="SchedulerServiceBehavior"> <serviceDebug includeExceptionDetailInFaults="true" /> <serviceThrottling maxConcurrentSessions="100"/> </behavior> </serviceBehaviors> </behaviors> </system.serviceModel> I've checked my firewall about a dozen times, but I guess there could be something I'm missing. Tried disabling windows firewall. I tried changing localhost to my ipv4 address to try to keep away from ipv6, I've tried removing any anti-ipv6 code.

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  • WCF net.tcp bindings, message formats and security questions

    - by RemotecUk
    Hi, sorry for the stupid questions but there are just some things about WCF I cant get my head around. Would be greatful for some advice on the following.... At a very basic level is it correct that WCF uses either Binary (Net.Tcp), HTTP or MSMQ to transfer my message on the wire? However is it true that in all cases, regardless of how the data is transferred the message itself in in the SOAP format with headers and a body? So its a sort of XML message that is transmitted in either HTTP/S or in a binary format. Is Net.Tcp a good choice for my client server app - its similar to a messenger app in that the clients are all remote users on the other side of the firewall to my server. Most things I am reading are telling to use WS* and HTTP. Is Net.Tcp secured by standard and without certificates? - that is - people cannot listen on the wire and decode the data thats going to and from. Is it possible to send a username and password using net.tcp and without an installed certificate? If so I presume I can hook this up to my membership provider and authenticate access to each method on my service contract implementation. I presume that with username and password security, the proxy is initialised with the username and password and that this information is is sent with every request. Then my membership provider will be invoked for each method call and do whatever it needs to do to get the authorisation for the method. Sorry for the dump of questions but would be great to know if Im thinking the right way about how WCF works. Thanks.

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  • Relation between HTTP Keep Alive duration and TCP timeout duration

    - by Suresh Kumar
    I am trying to understand the relation between TCP/IP and HTTP timeout values. Are these two timeout values different or same? Most Web servers allow users to set the HTTP Keep Alive timeout value through some configuration. How is this value used by the Web servers? is this value just set on the underlying TCP/IP socket i.e is the HTTP Keep Alive timeout and TCP/IP Keep Alive Timeout same? or are they treated differently? My understanding is (maybe incorrect): The Web server uses the default timeout on the underlying TCP socket (i.e. indefinite) regardless of the configured HTTP Keep Alive timeout and creates a Worker thread that counts down the specified HTTP timeout interval. When the Worker thread hits zero, it closes the connection. EDIT: My question is about the relation or difference between the two timeout durations i.e. what will happen when HTTP keep-alive timeout duration and the timeout on the Socket (SO_TIMEOUT) which the Web server uses is different? should I even worry about these two being same or not?

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  • TCP/IP Implementation General Questions

    - by user2971023
    I've implemented the concepts shown here; http://wiki.unity3d.com/index.php/Simple_TCP/IP_Client_-_Server outside of unity and it works. (though i had to create the TCPIPServerApp from scratch as i could not find the base project anywhere). I have some general questions on how to use tcp/ip properly however. I've done some research on tcp/ip itself but I'm still a little confused. It seems like using the method above doesn't guarantee that I'll see the message (res). It just checks on every update to see if there is a different message in res. What if multiple messages are sent and the program lags or something, will i miss the earlier packet(s)? Should i instead do an array so it stores the last X messages? How do i know the data was received? Do I need to add a message id and build in my own ack into the data? Should i check to see if the port is in use before setting up a connection? Sorry for all the questions. This is all new to me but I enjoy this very much! ... Below already answered By Anton, Thanks It sounds like tcp uses its own packet numbering to ensure the packets end up in the right order on the other side. What if a packet is missed, are the subsequent packets thrown away? Or is this numbering and packet ordering, only for handling data that is broken out into multiple packets? TCP will automatically break the data into multiple packets if necessary right?

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  • Unable to make 2 parallel TCP requests to the same TCP Client

    - by soldieraman
    Error: Unable to read data from the transport connection: A blocking operation was interrupted by a call to WSACancelBlockingCall Situation There is a TCP Server My web application connects to this TCP Server Using the below code: TcpClientInfo = new TcpClient(); _result = TcpClientInfo.BeginConnect(<serverAddress>,<portNumber>, null, null); bool success = _result.AsyncWaitHandle.WaitOne(20000, true); if (!success) { TcpClientInfo.Close(); throw new Exception("Connection Timeout: Failed to establish connection."); } NetworkStreamInfo = TcpClientInfo.GetStream(); NetworkStreamInfo.ReadTimeout = 20000; 2 Users use the same application from two different location to access information from this server at the SAME TIME Server takes around 2sec to reply Both Connect But One of the user gets above error "Unable to read data from the transport connection: A blocking operation was interrupted by a call to WSACancelBlockingCall" when trying to read data from stream How can I resolve this issue? Use a better way of connecting to the server Can't because it's a server issue if a server issue, how should the server handle request to avoid this problem

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