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• IPTables Rule for Google Apps SMTP

  - by XpresServers

  I am trying to add iptables rule to allow traffic on ports 465 & 587 to google apps smtp servers. But I got not luck. My WHMCS installation works fine with google apps when I turn off iptables but iptables turn on itself again and email stop working. Please add rules to allow traffic from port 465 and 587. Following are my IPTables rules grabbed from /etc/sysconfig/iptables # Generated by iptables-save v1.3.5 on Fri Oct 5 01:33:52 2012 *filter :INPUT ACCEPT [2191:434537] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [2390:987151] :acctboth - [0:0] -A INPUT -j acctboth -A OUTPUT -p tcp -m multiport --dports 25,465,587 -m owner --gid-owner mailman -j ACCEPT -A OUTPUT -p tcp -m multiport --dports 25,465,587 -m owner --gid-owner mail -j ACCEPT -A OUTPUT -d 127.0.0.1 -p tcp -m multiport --dports 25,465,587 -m owner --uid-owner cpanel -j ACCEPT -A OUTPUT -p tcp -m multiport --dports 25,465,587 -m owner --uid-owner root -j ACCEPT -A OUTPUT -j acctboth -A OUTPUT -o eth0 -p tcp -m tcp --sport 587 -m state --state ESTABLISHED -j ACCEPT -A OUTPUT -o eth0 -p tcp -m tcp --sport 465 -m state --state ESTABLISHED -j ACCEPT <<IN THIS SPACE RULES ARE RELATED TO SPECIFIC IPS ONLY>> -A acctboth -i ! lo COMMIT # Completed on Fri Oct 5 01:33:52 2012 # Generated by iptables-save v1.3.5 on Fri Oct 5 01:33:52 2012 *nat :PREROUTING ACCEPT [196:12398] :POSTROUTING ACCEPT [191:15070] :OUTPUT ACCEPT [190:15010] -A OUTPUT -p tcp -m multiport --dports 25,465,587 -m owner --gid-owner mailman -j RETURN -A OUTPUT -p tcp -m multiport --dports 25,465,587 -m owner --gid-owner mail -j RETURN -A OUTPUT -d 127.0.0.1 -p tcp -m multiport --dports 25,465,587 -m owner --uid-owner cpanel -j RETURN -A OUTPUT -p tcp -m multiport --dports 25,465,587 -m owner --uid-owner root -j RETURN -A OUTPUT -p tcp -m multiport --dports 25,465,587 -j REDIRECT COMMIT # Completed on Fri Oct 5 01:33:52 2012 Thanks Hassan

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• mount.nfs: access denied by server while mounting (Kerberos authentication)

  - by Nick

  There's plenty of references to this error on Goggle, and even a question here with the same title, but it seems that "access denied by server while mounting" is a catch-all error. I've tried suggestions that others have used to fix this problem, but they did not work in my case. I'm trying to set-up a Kerberos-based NFS file server with shared homes for a Linux network. I'm using Ubuntu 11.04 Servers and clients. When trying to mount a share using: mount 192.168.1.115:/export/home/ /media/tmp I get: mount.nfs: access denied by server while mounting 192.168.1.115:/export/home/ This is the same if I mount it from a client machine or from the server itself. On the server, in /var/log/syslog I get: Aug 25 06:22:37 nfs mountd[1580]: authenticated mount request from 192.168.1.115:835 for /export/home (/export/home) Aug 25 06:22:37 nfs mountd[1580]: authenticated unmount request from 192.168.1.115:766 for /export/home (/export/home) Which is odd, since it says it's authenticated the request, not denying it. /etc/exports: /export *(rw,fsid=0,crossmnt,insecure,async,no_subtree_check,sec=krb5p:krb5i:krb5) /export/home *(rw,insecure,async,no_subtree_check,sec=krb5p:krb5i:krb5) On client: me@dt1:/$ rpcinfo -p 192.168.1.115 program vers proto port 100000 2 tcp 111 portmapper 100024 1 udp 37320 status 100024 1 tcp 48460 status 100003 2 tcp 2049 nfs 100003 3 tcp 2049 nfs 100003 4 tcp 2049 nfs 100227 2 tcp 2049 100227 3 tcp 2049 100003 2 udp 2049 nfs 100003 3 udp 2049 nfs 100003 4 udp 2049 nfs 100227 2 udp 2049 100227 3 udp 2049 100021 1 udp 58625 nlockmgr 100021 3 udp 58625 nlockmgr 100021 4 udp 58625 nlockmgr 100021 1 tcp 49616 nlockmgr 100021 3 tcp 49616 nlockmgr 100021 4 tcp 49616 nlockmgr 100005 1 udp 45627 mountd 100005 1 tcp 60265 mountd 100005 2 udp 45627 mountd 100005 2 tcp 60265 mountd 100005 3 udp 45627 mountd 100005 3 tcp 60265 mountd Any suggestions I could try?

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• Sync Vs. Async Sockets Performance in C#

  - by Michael Covelli

  Everything that I read about sockets in .NET says that the asynchronous pattern gives better performance (especially with the new SocketAsyncEventArgs which saves on the allocation). I think this makes sense if we're talking about a server with many client connections where its not possible to allocate one thread per connection. Then I can see the advantage of using the ThreadPool threads and getting async callbacks on them. But in my app, I'm the client and I just need to listen to one server sending market tick data over one tcp connection. Right now, I create a single thread, set the priority to Highest, and call Socket.Receive() with it. My thread blocks on this call and wakes up once new data arrives. If I were to switch this to an async pattern so that I get a callback when there's new data, I see two issues The threadpool threads will have default priority so it seems they will be strictly worse than my own thread which has Highest priority. I'll still have to send everything through a single thread at some point. Say that I get N callbacks at almost the same time on N different threadpool threads notifying me that there's new data. The N byte arrays that they deliver can't be processed on the threadpool threads because there's no guarantee that they represent N unique market data messages because TCP is stream based. I'll have to lock and put the bytes into an array anyway and signal some other thread that can process what's in the array. So I'm not sure what having N threadpool threads is buying me. Am I thinking about this wrong? Is there a reason to use the Async patter in my specific case of one client connected to one server?

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• Sync Vs. Async Sockets Performance in .NET

  - by Michael Covelli

  Everything that I read about sockets in .NET says that the asynchronous pattern gives better performance (especially with the new SocketAsyncEventArgs which saves on the allocation). I think this makes sense if we're talking about a server with many client connections where its not possible to allocate one thread per connection. Then I can see the advantage of using the ThreadPool threads and getting async callbacks on them. But in my app, I'm the client and I just need to listen to one server sending market tick data over one tcp connection. Right now, I create a single thread, set the priority to Highest, and call Socket.Receive() with it. My thread blocks on this call and wakes up once new data arrives. If I were to switch this to an async pattern so that I get a callback when there's new data, I see two issues The threadpool threads will have default priority so it seems they will be strictly worse than my own thread which has Highest priority. I'll still have to send everything through a single thread at some point. Say that I get N callbacks at almost the same time on N different threadpool threads notifying me that there's new data. The N byte arrays that they deliver can't be processed on the threadpool threads because there's no guarantee that they represent N unique market data messages because TCP is stream based. I'll have to lock and put the bytes into an array anyway and signal some other thread that can process what's in the array. So I'm not sure what having N threadpool threads is buying me. Am I thinking about this wrong? Is there a reason to use the Async patter in my specific case of one client connected to one server?

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• Workflow engine BPMN, Drools, etc or ESB?

  - by Tom

  We currently have an application that is based on an in-house developed workflow engine with YAML based DSL. We are looking to move parts of it to Java. I have discovered a number of java solutions like Intalio, JBPM, Drools Expert, Drools Flow etc. They appear to be aimed at businesses where the business analyst creates the workflows using a graphical editor and submits them to the workflow engine. They seem geared towards ease of use for non-technical people rather than for developers with a focus on human interaction. The workflows tend to look like. Discover-a-file -\ -> join -> process-file -> move-file -> register-file Discover-some-metadata -/ If any step fails we need to retry it X times. We also need to be able to stop the system and be able to restart it and have it continue from where it was (durable). Some of our workflows can be defined by a set of goals we need to achieve so Jess's backwards rule chaining sounds interesting but it is not open source. It might be that what we are after is a Finite State Machine engine or just an Enterprise Service Bus and do everything as JMS queues. Is there a good open source workflow engine that is both standards-based but also geared towards developers. We don't particular want to use a graphical workflow designer or write reams of XML and it should ideally be in Java or language agnostic (makes REST/Soap calls to external services). Thanks, Tom

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• Is it possible to make a persistent connection between a Python web service and a .Net WCF Client?

  - by Ad Hock

  I have a .Net 3.5 SOAP client written in C# using the WCF. It's expecting basicHTTPBinding and a persistent connection with HTTP/1.1. I'm trying to create a Python 2.6 application that will act as a web-service for the client. My problem is that the client keeps closing the connection and opening a new one for every command to the web service. How does the .Net WCF client know to stay open when connecting with a .Net Service? When I create a dummy .Net web service the client connects fine and the connection remains persistent. From what I can tell, when connected to a .Net server, there are no special HTTP headers being sent, that makes sense since HTTP/1.1 assumes a persistent connection unless otherwise specified (right?). However, with the python web service I accept/open a connection and eventually the client will send a TCP FIN and the connection will close (the client never sends a FIN or RST when connecting to a .Net service). The communication goes something like this: Incoming -- HTTP Header for SOAP Command #1 Outgoing -- HTTP Header with a Continue Incoming -- Body of Command #1 Outgoing -- ACK Command #1 (HTTP headers and body) Incoming -- HTTP Header for SOAP Command #2 Outgoing -- HTTP Header with a Continue Incoming -- TCP FIN <Connection closes> <New connection opens and SOAP command #2 (with full HTTP headers) is sent> I'm using a SocketServer.ThreadingTCPServer as the server and a BaseHTTPServer.BaseHTTPRequestHandler for any requests. The handler is actually a derived class of that with a do_POST method to handle the HTTP headers. I've looked at WireShark captures and I'm stumped. I've tried setting socket options to SO_KEEPALIVE and SO_REUSEADDR in the server but that didn't seem to change anything. What am I missing?

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• How does the socket API accept() function work?

  - by Eli Bendersky

  The socket API is the de-facto standard for TCP/IP and UDP/IP communications (that is, networking code as we know it). However, one of its core functions, accept() is a bit magical. To borrow a semi-formal definition: accept() is used on the server side. It accepts a received incoming attempt to create a new TCP connection from the remote client, and creates a new socket associated with the socket address pair of this connection. In other words, accept returns a new socket through which the server can communicate with the newly connected client. The old socket (on which accept was called) stays open, on the same port, listening for new connections. How does accept work? How is it implemented? There's a lot of confusion on this topic. Many people claim accept opens a new port and you communicate with the client through it. But this obviously isn't true, as no new port is opened. You actually can communicate through the same port with different clients, but how? When several threads call recv on the same port, how does the data know where to go? I guess it's something along the lines of the client's address being associated with a socket descriptor, and whenever data comes through recv it's routed to the correct socket, but I'm not sure. It'd be great to get a thorough explanation of the inner-workings of this mechanism.

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• Precompile assets for a rails engine

  - by Peter Ehrlich

  In a standard app, I have this line in my production.rb, which creates endpoints for non-default precompiled assets: config.assets.precompile += %w( mobile.css ) My rails engine is a standard Sinatra app. It has its own assets. When on development, these assets are served fine, presumably the web requests are handled by rails and sprockets. On production I'm getting 404s on the assets, and think I have to manually tell sprockets to provide the files. How can this be done without tightly linking? It isin't evident how to set up env-specific initializers for engines. Is this done? Not only, for example, is config/development.rb within the engine not loaded, but there's no way to get the application class itself without knowing its name, in order to modify configuration. And even if there was, it seems that having any engine able to reconfigure the main app would be very bad idea. So maybe its better to let assets handling be done by sinatra itself? Or another instance of sprockets for the engine? How do other engines handle this?

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• MySQL " identify storage engine statement"

  - by sammysmall

  This IS NOT a Homework question! While building my current student database project I realized that I may want to identify comprehensive information about a database design in the future. More-so if I am fortunate enough to get a job in this field and were handed a database project how could I break down certain elements for identification... In all of my previous designs I have been using MySQL Community Server (GPL) 5.1.42, I thought (duh) that I was using the MyISAM based on most of my text-book instruction and MySQL 5.0 Reference Manual :: 13 Storage Engines :: 13.1 The MyISAM Storage Engine I determined that this was in fact incorrect for this version and the use of "SHOW ENGINES" at the console... No problem, figured out why they have "versions" the need to pay attention to what version is being used, and the need for a means to determine what I am about to mess up "if" I do not pay attention to detail... Q1. Specifically what statement will identify the version used by someone elses initial database creation? (since I created my own databases I know what version I used) Q2. Specifically what statement will identify the storage engine that the developer used when creating the database. (I specified a particular database in my collection then tried SHOW Engine, did not work, then tried to just get the metadata from one table in that database: mysql SELECT duck_cust, table_type, engine - FROM INFORMATION_SCHEMA.tables - WHERE table_schema = 'tp' - ORDER BY table_type ASC, table_name DESC; as this was not really what I wanted (and did not work) I am looking for some direction from the pros... Q3. (If you really have the inclination to continue helping) If I were to access a database from an earlier/later "version" are there backward/forward compatibility issues for maintaining/updating data between versions? Please and Thank you in advance for your time and efforts! sammysmall

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• What does LAST_ACK mean, as a State value in netstat?

  - by nbolton

  If a Windows server has several thousand ports open in LAST_ACK state (as shown by netstat), what could this mean? Is it because one endpoint is waiting for the other to respond?

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• ICMP Redirect Theory VS. Application

  - by joeqwerty

  I'm trying to watch ICMP redirects in a lab using Cisco Packet Tracer (version 5.3.2) and I'm not seeing them, which leads me to believe that either my lab configuration isn't correct or my understanding of ICMP redirects isn't correct or that Packet Tracer doesn't support/use ICMP redirects. Here's what I believe to be true regarding ICMP redirects: Routers send ICMP redirects when all of these conditions are met: The interface on which the packet comes into the router is the same interface on which the packet gets routed out. The subnet or network of the source IP address is on the same subnet or network of the next-hop IP address of the routed packet. The datagram is not source-routed. The router kernel is configured to send redirects. I have the lab set up in Cisco Packet Tracer as displayed in the image and would expect to see an ICMP redirect from Router1 when pinging from PC1 to PC3. I'm not seeing the ICMP redirect and it looks like Router1 is actually routing all of the packets via Router2. I have IP ICMP debugging enabled on Router1 (and Router2) and I'm not seeing any ICMP redirect activity in either console. I'm also not seeing a route to the PC3 network in the routing table on PC1, which I think confirms that the ICMP redirect is not occurring. I'm using only static routing on Routers 1 and 2. Is my understanding of ICMP redirects incorrect, or is there a problem with my lab configuration or does Packet Tracer not support/use ICMP redirects?

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• Socket(TCPIP) Unstable

  - by Lee Kwan Wee

  I have a setup of a SCPI server in a Win7 PC and have 2 other programs talking to it locally(127.0.0.1) over TCPIP socket 5025 and 5029. This worked well and stable in a fresh PC, but when we moved it into our production lines and the IT dept added their policies and stuff, it became unstable. The PC is connected to the production floor server but both of the programs are running locally in the PC. The connection tends to be disconnected when there is an idle period. And it takes 5-6times to refreshing the connection to get it back. I'm not a programmer myself, so I'm hoping to see if anyone here can help with some answers. Thank you very much!! Regards, KwanWee.

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• iptables not allowing mysql connections to aliased ips?

  - by Curtis

  I have a fairly simple iptables firewall on a server that provides MySQL services, but iptables seems to be giving me very inconsistent results. The default policy on the script is as follows: iptables -P INPUT DROP I can then make MySQL public with the following rule: iptables -A INPUT -p tcp --dport 3306 -j ACCEPT With this rule in place, I can connect to MySQL from any source IP to any destination IP on the server without a problem. However, when I try to restrict access to just three IPs by replacing the above line with the following, I run into trouble (xxx=masked octect): iptables -A INPUT -p tcp --dport 3306 -m state --state NEW -s 208.XXX.XXX.184 -j ACCEPT iptables -A INPUT -p tcp --dport 3306 -m state --state NEW -s 208.XXX.XXX.196 -j ACCEPT iptables -A INPUT -p tcp --dport 3306 -m state --state NEW -s 208.XXX.XXX.251 -j ACCEPT Once the above rules are in place, the following happens: I can connect to the MySQL server from the .184, .196 and .251 hosts just fine as long as am connecting to the MySQL server using it's default IP address or an IP alias in the same subnet as the default IP address. I am unable to connect to MySQL using IP aliases that are assigned to the server from a different subnet than the server's default IP when I'm coming from the .184 or .196 hosts, but .251 works just fine. From the .184 or .196 hosts, a telnet attempt just hangs... # telnet 209.xxx.xxx.22 3306 Trying 209.xxx.xxx.22... If I remove the .251 line (making .196 the last rule added), the .196 host still can not connect to MySQL using IP aliases (so it's not the order of the rules that is causing the inconsistent behavior). I know, this particular test was silly as it shouldn't matter what order these three rules are added in, but I figured someone might ask. If I switch back to the "public" rule, all hosts can connect to the MySQL server using either the default or aliased IPs (in either subnet): iptables -A INPUT -p tcp --dport 3306 -j ACCEPT The server is running in a CentOS 5.4 OpenVZ/Proxmox container (2.6.32-4-pve). And, just in case you prefer to see the problem rules in the context of the iptables script, here it is (xxx=masked octect): # Flush old rules, old custom tables /sbin/iptables --flush /sbin/iptables --delete-chain # Set default policies for all three default chains /sbin/iptables -P INPUT DROP /sbin/iptables -P FORWARD DROP /sbin/iptables -P OUTPUT ACCEPT # Enable free use of loopback interfaces /sbin/iptables -A INPUT -i lo -j ACCEPT /sbin/iptables -A OUTPUT -o lo -j ACCEPT # All TCP sessions should begin with SYN /sbin/iptables -A INPUT -p tcp ! --syn -m state --state NEW -j DROP # Accept inbound TCP packets (Do this *before* adding the 'blocked' chain) /sbin/iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT # Allow the server's own IP to connect to itself /sbin/iptables -A INPUT -i eth0 -s 208.xxx.xxx.178 -j ACCEPT # Add the 'blocked' chain *after* we've accepted established/related connections # so we remain efficient and only evaluate new/inbound connections /sbin/iptables -N BLOCKED /sbin/iptables -A INPUT -j BLOCKED # Accept inbound ICMP messages /sbin/iptables -A INPUT -p ICMP --icmp-type 8 -j ACCEPT /sbin/iptables -A INPUT -p ICMP --icmp-type 11 -j ACCEPT # ssh (private) /sbin/iptables -A INPUT -p tcp --dport 22 -m state --state NEW -s xxx.xxx.xxx.xxx -j ACCEPT # ftp (private) /sbin/iptables -A INPUT -p tcp --dport 21 -m state --state NEW -s xxx.xxx.xxx.xxx -j ACCEPT # www (public) /sbin/iptables -A INPUT -p tcp --dport 80 -j ACCEPT /sbin/iptables -A INPUT -p tcp --dport 443 -j ACCEPT # smtp (public) /sbin/iptables -A INPUT -p tcp --dport 25 -j ACCEPT /sbin/iptables -A INPUT -p tcp --dport 2525 -j ACCEPT # pop (public) /sbin/iptables -A INPUT -p tcp --dport 110 -j ACCEPT # mysql (private) /sbin/iptables -A INPUT -p tcp --dport 3306 -m state --state NEW -s 208.xxx.xxx.184 -j ACCEPT /sbin/iptables -A INPUT -p tcp --dport 3306 -m state --state NEW -s 208.xxx.xxx.196 -j ACCEPT /sbin/iptables -A INPUT -p tcp --dport 3306 -m state --state NEW -s 208.xxx.xxx.251 -j ACCEPT Any ideas? Thanks in advance. :-)

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• TIME_WAIT connections not being cleaned up after timeout period expires

  - by Mark Dawson

  I am stress testing one of my servers by hitting it with a constant stream of new network connections, the tcp_fin_timeout is set to 60, so if I send a constant stream of something like 100 requests per second, I would expect to see a rolling average of 6000 (60 * 100) connections in a TIME_WAIT state, this is happening, but looking in netstat (using -o) to see the timers, I see connections like: TIME_WAIT timewait (0.00/0/0) where their timeout has expired but the connection is still hanging around, I then eventually run out of connections. Anyone know why these connections don't get cleaned up? If I stop creating new connections they do eventually disappear but while I am constantly creating new connections they don't, seems like the kernel isn't getting chance to clean them up? Is there some other config options I need to set to remove the connections as soon as they have expired? The server is running Ubuntu and my web server is nginx. Also it has iptables with connection tracking, not sure if that would cause these TIME_WAIT connections to live on. Thanks Mark.

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• calling a different python interpreter from bash command line

  - by Dennis Daniels

  I have python 2.7 installed [user@localhost google_appengine]$ python Python 2.7 (r27:82500, Sep 16 2010, 18:03:06) [GCC 4.5.1 20100907 (Red Hat 4.5.1-3)] on linux2 Type "help", "copyright", "credits" or "license" for more information. I want to use the python 2.5.2 that is in this directory [user@localhost Downloads]$ ls |grep "Python-2*" Python-2.5.2 Python-2.5.2.tgz to run a python script in Khan Academy platform against a google app engine application sudo python sample_data.py -a ~/workspace/GAE/google_appengine/appcfg.py upload Currently, when running the last script 2.7 python complains a lot (Google App Engine runs on 2.5.2 mostly and 2.6 almost) I would like to do something like sudo python env set ~/Downloads/Python-2.5.2 sample_data.py -a ~/workspace/GAE/google_appengine/appcfg.py upload Is this possible? If yes, please point the way. If not, please suggest a way to call python2.5.2 WITHOUT having to uninstall python 2.7 many many thanks Dennis

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• (OS 10055) Queue full

  - by Ali

  I'm using apache with mysql on the other server, apache on windows 2003 with 4gb ram 3 dual core CPU My server keep on running smoothly without any issue for about 3 days or roundabout 60+ hours however between 60-70 hours my apache stop working & log events shows this error, I tried to search a lot but helpless, I have already increased max port, please if someone can help ? (OS 10055)An operation on a socket could not be performed because the system lacked sufficient buffer space or because a queue was full. : make_sock: unable to listen for connections on address 0.0.0.0:80

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• How to troubleshoot connectivity when curl gets an *empty response*

  - by chad

  I want to know how to proceed in troubleshooting why a curl request to a webserver doesn't work. I'm not looking for help that would be dependent upon my environment, I just want to know how to collect information about exactly what part of the communication is failing, port numbers, etc. chad-integration:~ # curl -v 111.222.159.30 * About to connect() to 111.222.159.30 port 80 (#0) * Trying 111.222.159.30... connected * Connected to 111.222.159.30 (111.222.159.30) port 80 (#0) > GET / HTTP/1.1 > User-Agent: curl/7.19.0 (x86_64-suse-linux-gnu) libcurl/7.19.0 OpenSSL/0.9.8h zlib/1.2.3 libidn/1.10 > Host: 111.222.159.30 > Accept: */* > * Empty reply from server * Connection #0 to host 111.222.159.30 left intact curl: (52) Empty reply from server * Closing connection #0 So, I understand that an empty response means that curl didn't get any response from the server. No problem, that's precisely what I'm trying to figure out. But what more specific info can I derive from cURL here? It was able to successfully "connect", so doesn't that involve some bidirectional communication? If so, then why does the response not come also? Note, I've verified my service is up and returning responses. Note, I'm a bit green at this level of networking, so feel free to provide some general orientation material.

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• server will not reply (syn -ack)

  - by Brent

  I like to use the following commands to manage 'TIME_WAIT', in the hope to free up resources. echo 20 > /proc/sys/net/ipv4/tcp_fin_timeout sysctl -w net.ipv4.tcp_tw_reuse=1 sysctl -w net.ipv4.tcp_tw_recycle=1 I found something interesting while doing a tcpdump. Sometimes if a client makes a connection (syn), the server will not reply (syn -ack). My question is, could it be because of the top three commands.

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• SYN flooding still a threat to servers?

  - by Rob

  Well recently I've been reading about different Denial of Service methods. One method that kind of stuck out was SYN flooding. I'm a member of some not-so-nice forums, and someone was selling a python script that would DoS a server using SYN packets with a spoofed IP address. However, if you sent a SYN packet to a server, with a spoofed IP address, the target server would return the SYN/ACK packet to the host that was spoofed. In which case, wouldn't the spoofed host return an RST packet, thus negating the 75 second long-wait, and ultimately failing in its attempt to DoS the server?

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• redirect all youtube video requests to a specific one

  - by iTayb

  I'm on an IT team in my company and I would like to block youtube to users. I don't want to just deny access to the whole youtube domain, but only to replace the .flv/.mp4 request with the one that I want. That way, if someone tries to watch youtube videos on the network, He'll get a video of why using our expensive bandwidth for pleasure is a no-no. I thought about using a packet manipulation program and just replace the video ID with something that I want, but I didn't manage to do it right.

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• Connection to mysql server in SYN_SENT

  - by Sunil

  We are facing a strange problem from last few days between our application server and database server(Mysql): connection to database server from application server hangs in SYN_SENT state and after that we are not able to make any connection to database server on mysql port(3306). When we checked the netstat output on database server its in SYN_RECV state. What I can figure out is mysql server is receiving the SYN request and responding also and its not reaching to the client hence SYN_RECV at server side and SYN_SENT at client side. I think SYN_SENT state should go after some time and because of this other db connection attempts to same server should not hang. Does anybody have any idea how can we resolve this issue? Out setup details : Application server: RHEL 5.4, kernel-release = 2.6.18-164.el5, x86_64 Database server: Mysql Version : 5.1.49 RHEL 5.4, kernel-release = 2.6.18-164.el5, x86_64

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• Web application/ site service (like Google App Engine) for PHP/ MySQL and Postgres

  - by Simon

  I would like to find a service similar to Google App Engine for PHP/ MySQL/ Postgres sites/ applications. We host two different types of site. i). PHP/ Mysql/ Zend Framework <VirtualHost *:80> DocumentRoot "/home/websites/website.com/public" ServerName website.com # This should be omitted in the production environment SetEnv APPLICATION_ENV development <Directory "/home/websites/website.com/public"> Options Indexes MultiViews FollowSymLinks AllowOverride All Order allow,deny Allow from all RewriteEngine On RewriteCond %{REQUEST_FILENAME} -s [OR] RewriteCond %{REQUEST_FILENAME} -l [OR] RewriteCond %{REQUEST_FILENAME} -d RewriteRule ^.*$ - [NC,L] RewriteRule ^.*$ index.php [NC,L] </Directory> </VirtualHost> ii). Matrix CMS - PHP/ Postgres + loads of pear classes <VirtualHost *:80> ServerName server.example.com DocumentRoot /home/websites/mysource_matrix/core/web Options -Indexes FollowSymLinks <Directory /home/websites/mysource_matrix> Order deny,allow Deny from all </Directory> <DirectoryMatch "^/home/websites/mysource_matrix/(core/(web|lib)|data/public|fudge)"> Order allow,deny Allow from all </DirectoryMatch> <DirectoryMatch "^/home/websites/mysource_matrix/data/public/assets"> php_flag engine off </DirectoryMatch> <FilesMatch "\.inc$"> Order allow,deny Deny from all </FilesMatch> <LocationMatch "/(CVS|\.FFV)/"> Order allow,deny Deny from all </LocationMatch> Alias /__fudge /home/websites/mysource_matrix/fudge Alias /__data /home/websites/mysource_matrix/data/public Alias /__lib /home/websites/mysource_matrix/core/lib Alias / /home/websites/mysource_matrix/core/web/index.php/ </VirtualHost> My key requirements are: I don't want to worry/ know/ care about the server/ infrastructure Secure/ up to date software/ os Good monitoring Automatic scalability SLA I apologise for the length of the question. In short all I want to do is i). create vhost, ii). create db iii). install app/ site iv). relax. Thanks. Edit: I include the Matrix vhost because that is the only complication that I cannot really do via a .htaccess file.

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• tcpsndbuf high fail count

  - by Matthew Crenshaw

  I've got a small setup, one machine that acts as a load balancer and two machines that do all the work. The load balancer runs nginx (static content + php proxying to workers) and mysql, the two workers run php5-fpm and memcached (pooled between workers). Here's beancounters for the balancer: tcpsndbuf 2171848 2386280 10000000 20000000 3947733 tcprcvbuf 1248288 1669504 10000000 20000000 0 Here's worker 1: tcpsndbuf 951976 1262672 20000000 40000000 0 tcprcvbuf 278528 393496 20000000 40000000 0 Here's worker 2: tcpsndbuf 989888 527472 20000000 40000000 0 tcprcvbuf 212992 452520 20000000 40000000 0 The balancer has 1GB ram, the two workers have 2GB ram each. What is eating my send buffer?

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• pfSense router on a LAN with two gateways

  - by JohnCC

  I have a LAN with an ADSL modem/router on it. We have just gained an alternative high-speed internet connection at our location, and I want to connect the LAN to it, eventually dropping the ADSL. I've chosen to use a small PFSense box to connect the LAN to the new WAN connection. Two servers on the LAN run services accessible to the outside via NAT using the single ADSL WAN IP. We have DNS records which point to this IP. I want to do the same via the new connection, using the WAN IP there. That connection permits multiple IPs, so I have configured pfSense using virtual IP's, 1:1 NAT and appropriate firewall rules. When I change the servers' default gateway settings to the pfSense box, I can access the services via the new WAN IPs without a problem. However, I can no longer access them via the old WAN IP. If I set the servers' default gateway back to the ADSL router, then the opposite is true - I can access the services via the ADSL IP, but not via the new one. In the first case, I believe this is because an incoming SYN packet arrives at the ADSL WAN IP, and is NAT'd and sent to the internal IP of the server. The server responds with a SYN/ACK which it sends via its default gateway, the pfSense box. The pfSense box sees a SYN/ACK that it saw no SYN for and drops the packet. Is there any sensible way around this? I would like the services to be accessible via both IPs for a short period at least, since once I change the DNS it will take a while before everyone picks up the new address.

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• Access Methods to a computer Using MAC Address

  - by Dimal Chandrasiri

  I have my own wifi network at home & recently when I checked the active clients on the wifi I found out the there is one active client. Router shows the MAC address of this client and I want to Access this computer in order to let him know that he's doing a wrong thing. I dont intent to do any harm to his data. I just want to know a method to send him a message saying "Buy you own wifi". How can I achieve this using a windows 8 computer. Is there any specific softwares that I can use or will the netsend command do the trick! Thank you.

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