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• Reading data from a socket, considerations for robustness and security

  - by w.brian

  I am writing a socket server that will implement small portions of the HTTP and the WebSocket protocol, and I'm wondering what I need to take into consideration in order to make it robust/secure. This is my first time writing a socket-based application so please excuse me if any of my questions are particularly naive. Here goes: Is it wrong to assume that you've received an entire HTTP request (WebSocket request, etc) if you've read all data available from the socket? Likewise, is it wrong to assume you've only received one request? Is TCP responsible for making sure I'm getting the "message" all at once as sent by the client? Or do I have to manually detect the beginning and end of each "message" for whatever protocol I'm implementing? Regarding security: What, in general, should I be aware of? Are there any common pitfalls when implementing something like this? As always, any feedback is greatly appreciated.

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• Detect aborted connection during ASIO request

  - by Tim Sylvester

  Is there an established way to determine whether the other end of a TCP connection is closed in the asio framework without sending any data? Using Boost.asio for a server process, if the client times out or otherwise disconnects before the server has responded to a request, the server doesn't find this out until it has finished the request and generated a response to send, when the send immediately generates a connection-aborted error. For some long-running requests, this can lead to clients canceling and retrying over and over, piling up many instances of the same request running in parallel, making them take even longer and "snowballing" into an avalanche that makes the server unusable. Essentially hitting F5 over and over is a denial-of-service attack. Unfortunately I can't start sending a response until the request is complete, so "streaming" the result out is not an option, I need to be able to check at key points during the request processing and stop that processing if the client has given up.

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• How to gain greater control of network packets on Android

  - by mauvehead

  I'm looking to design an application that will require some deep control over IP packets. Looking over the reference guide on the developers site at Android I see very limited control over packets from java.net:SocketOptions and java.net:DatagramPacket. Specifically I'm looking to control the individual bits within the packet to set TCP Flags, SYN/ACK/RST, and so forth. Based on the docs I am assuming I cannot do this within the Java API provided by Android and I'm guessing I'll have to do it some other way? Anyone have any insight on this?

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• Why isn't Hadoop implemented using MPI?

  - by artif

  Correct me if I'm wrong, but my understanding is that Hadoop does not use MPI for communication between different nodes. What are the technical reasons for this? I could hazard a few guesses, but I do not know enough of how MPI is implemented "under the hood" to know whether or not I'm right. Come to think of it, I'm not entirely familiar with Hadoop's internals either. I understand the framework at a conceptual level (map/combine/shuffle/reduce and how that works at a high level) but I don't know the nitty gritty implementation details. I've always assumed Hadoop was transmitting serialized data structures (perhaps GPBs) over a TCP connection, eg during the shuffle phase. Let me know if that's not true.

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• Building a webserver, client doesn't acknowledge HTTP 200 OK frame.

  - by Evert

  Hi there, I'm building my own webserver based on a tutorial. I have found a simple way to initiate a TCP connection and send one segment of http data (the webserver will run on a microcontroller, so it will be very small) Anyway, the following is the sequence I need to go through: receive SYN send SYN,ACK receive ACK (the connection is now established) receive ACK with HTTP GET command send ACK send FIN,ACK with HTTP data (e.g 200 OK) receive FIN,ACK <- I don't recieve this packet! send ACK Everything works fine until I send my acknowledgement and HTTP 200 OK message. The client won't send an acknowledgement to those two packages and thus no webpage is being displayed. I've added a pcap file of the sequence how I recorded it with wireshark. Pcap file: http://cl.ly/5f5 (now it's the right data) All sequence and acknowledgement numbers are correct, checksum are ok. Flags are also right. I have no idea what is going wrong.

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• paket drop and splits in udp tunnel

  - by sr-dusad

  hi guys ! Currently I am working on video conferencing project.For this i m using pwnat for nat traversing. pwnat is based on udp tunneling.I m using the TCP connection for data transmission. My problem is that when i send a packet , it does not reach properly at its destination side . Sometime it drops the packet and many times it breaks ( split ) the packet into pieces. Please Help me .. How can i send and recieve a packet into single piece. So, i can draw image properly and play sound. Any kind of help will be appriciated . Thanks in advance

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• "Can´t open socket or connection refused" with .NET

  - by HoNgOuRu

  Im getting a connection refused when I try to send some data to my server app using netcat. server side: IPAddress ip; ip = Dns.GetHostEntry("localhost").AddressList[0]; IPEndPoint ipFinal = new IPEndPoint(ip, 12345); Socket socket = new Socket(AddressFamily.InterNetworkV6, SocketType.Stream, ProtocolType.Tcp); socket.Bind(ipFinal); socket.Listen(100); Socket handler = socket.Accept(); ------> it stops here......nothing happens

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• Python, implementing proxy support for a socket based application (not urllib2)

  - by Terry Felkrow

  Hey guys, I am little stumped: I have a simple messenger client program (pure python, sockets), and I wanted to add proxy support (http/s, socks), however I am a little confused on how to go about it. I am assuming that the connection on the socket level will be done to the proxy server, at which point the headers should contain a CONNECT + destination IP (of the chat server) and authentication, (if proxy requires so), however the rest is a little beyond me. How is the subsequent connection handled, specifically the reading/writing, etc... Are there any guides on proxy support implementation for socket based (tcp) programming in Python? Thank you

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• Count of memory copies in *nix systems between packet at NIC and user application?

  - by Michael_73

  Hi there, This is just a general question relating to some high-performance computing I've been wondering about. A certain low-latency messaging vendor speaks in its supporting documentation about using raw sockets to transfer the data directly from the network device to the user application and in so doing it speaks about reducing the messaging latency even further than it does anyway (in other admittedly carefully thought-out design decisions). My question is therefore to those that grok the networking stacks on Unix or Unix-like systems. How much difference are they likely to be able to realise using this method? Feel free to answer in terms of memory copies, numbers of whales rescued or areas the size of Wales ;) Their messaging is UDP-based, as I understand it, so there's no problem with establishing TCP connections etc. Any other points of interest on this topic would be gratefully thought about! Best wishes, Mike

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• Efficient multiple services exposed over c# .NET remoting using more channels or end points?

  - by wb

  I am using remoting over TCP for a prototype distributed server application where I want to have varying multiple services exposed from each remoting server process. In some cases I want the services running from the same process but I don't want whatever is using the service to care about that. I am wondering is it more efficient to have multiple services in the same process going over the same remoting channel distinguished by endpoint URI/URL or should I be creating new channels on different ports for each service in the same process? Using up ports isn't so much of a problem as the number of services will be low and the network and machine configuration is completely controlled. Also its not clear to me if remoting sends the URI string for every single message or just at connection time, and whether if the remoting framework is intelligent enough to reduce work if calls are made on the same machine and even the same process? Thanks in advance.

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• Terminate an inactive socket connection from TIdTCPServer

  - by A.J.

  We have an application which listens for incoming TCP requests using the Indy 10.1.1 components that ship with Delphi 2007. Occassionally we receive incoming connections which are not from our client application. Typically, one of two things happens: 1) the connection is terminated by the client before any data is received, or 2) data is received which we're not expecting and we manually terminate the connection. However, we've received connections where no data is received and appear to persist until the client terminates the connection from their end. Is there a way to terminate such a connection from the server if no data is received after a specified amount of time?

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• Troubleshooting occasional timeout of select() in windows

  - by JonF

  I'm having an occasional problem with select() timing out on me. I have it set for twenty seconds. The system will handle 100's of transactions correctly, but occasionally one fails with the selet timing out. It does about 1 transaction every few seconds, opening and closing the tcp conncetion with each transaction. I thought the server my app was connecting to might have to many connection attempts pending, but no 4226 events are showing up in the logs One more point thing I noticed when using wireshark that I'm getting a SYN,RST in response to the SYN I am appearently sending. This only happens a few times over the first second or two, then I don't see any more activity in Wireshark

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• Sql server management studio reporting "The semaphore timeout period has expired."

  - by nis-simonsen

  On our development sql server, executing any query containing more than approximately 700 characters stalls for about 10 seconds and then reports the following error: Msg 121, Level 20, State 0, Line 0 A transport-level error has occurred when receiving results from the server. (provider: TCP Provider, error: 0 - The semaphore timeout period has expired.) for example, this query select * from FooTable where id = ' (.. and then 700 spaces ..) ' fails fails with the timeout error while this one select * from FooTable where id = ' (.. and then 600 spaces ..) ' fails with the expected Msg 8169, Level 16, State 2, Line 1 Conversion failed when converting from a character string to uniqueidentifier. - immediately. Indeed, throwing any query, including random garbage at our dev sql server exhibits this behaviour, while any other sql server I have available acts as expected, so I would think that the query never actually gets to parsing on the server. I'm at a loss here - any hints?

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• How to difference sockaddr_in struct from same subnetwork and different IP/users

  - by user1428926

  I am developing a gaming server using the Winsock2 API from Windows, just for now until porting it to Linux. The main problem I have found is that I don't know how to differentiate gaming clients that come from the same router/network. Let´s imagine 2 gamers that are in the same network going to the Internet through the same router IP and port with, for example IP 220.100.100.100 and port 5000, how can my C/C++ server differentiate both TCP connections and know that they are two different gamers? Can I find any difference in the sockaddr_in struct that returns the socket when accept(...) returns ??

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• What library to use to create a simple port scanner?

  - by durje

  I need advise to create a simple port-scanner, who will need to detect if some specific devices are connected to the network from theire IP/MAC address. I am working on windows 7 and can use preferably C++ Builder 2010 Embarcadero, or java or Qt. The library have to be under a public domain or equivalent, as my software is a proprietary software. What library would you advice? Do you know any free software that I could start from, or any examples? What about using Indy Sockets or Synapse TCP/IP Librarys? Thanks in advance.

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• Intercommunication between Java Chat Servers

  - by Pravingate

  I have a application in which I am using socket programming , having this(image) scenario. Where number of clients will try to connect Broadcast server. Now here I am managing load through LVS(Load balancer). so as a example shown in image, suppose 200 clients will wish to login for broadcast they will be distributed as 100 users on server 1 and another 100 users on server 2.clients will get connected to servers using TCP connection. Now I am maintaining user information on server side in arraylist which will be stored in heap memory,Now the problem is if client wish to broadcast to all logged in users, but that particular client is logged in server 1. and so client will not be able to broadcast another 100 users from server 2. Because both ther servers are unaware about each others state. please suggest to solve this scenario by whatever means you want.

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• 16 millisecond quantization when sending/receivingtcp packets

  - by MKZ

  Hi, I have a C++ application running on windows xp 32 system sending and receiving short tcp/ip packets. Measuring (accurately) the arrival time I see a quantization of the arrival time to 16 millisecond time units. (Meaning all packets arriving are at (16 )xN milliseconds separated from each other) To avoid packet aggregation I tried to disable the NAGLE algorithm by setting the IPPROTO_TCP option to TCP_NODELAY in the socket variables but it did not help I suspect that the problem is related to the windows schedular which also have a 16 millisecond clock.. Any idea of a solution to this problem ? Thanks

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• Forking with a listening socket

  - by viraptor

  I'd like to make sure about the correctness of the way I try to use accept() on a socket. I know that in Linux it's safe to listen() on a socket, fork() N children and then recv() the packets in all of them without any synchronisation from the user side (the packets get more or less load-balanced between the children). But that's UDP. Does the same property hold for TCP and listen(), fork(), accept()? Can I just assume that it's ok to accept on a shared socket created by the parent, even when other children do the same? Is POSIX, BSD sockets or any other standard defining it somewhere?

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• How to turn one server into many servers? (Virtualization/VMWare)

  - by user1229962

  I'm hoping for a high level discussion of this problem I know is quickly approaching my application. I have a server that binds on a specific port and manages TCP Sockets from my clients. I know that it is common practice to use VMWare to virtualize servers and run multiple servers at once. How can a single server design be changed to support multiple servers? Multiple servers can't bind to the same port. If I had to guess I would say a proxy server binds to the port and then sends connections off to the other servers to be handled as if it was still a single server application. I'm wondering what options there are and what are the common practices for solving this problem? Thanks in advance!

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• after enabling mod ssl apache stops listening on port 80

  - by zensys

  I have an ubuntu 12.04 server with zend server CE installed. I now wanted to enable https but after the first steps according to the documentation, 'a2enmod ssl' and 'apache service restart', apache does not listen on 443 but neither on 80, according to netstat -tap | grep http(s)! This is what I see in my error log, but I can't make much of it: [Fri May 25 19:52:39 2012] [notice] caught SIGTERM, shutting down [Fri May 25 19:52:41 2012] [warn] Init: Session Cache is not configured [hint: SSLSessionCache] [Fri May 25 19:52:41 2012] [notice] ModSecurity for Apache/2.6.3 (http://www.modsecurity.org/) configured. [Fri May 25 19:52:41 2012] [notice] ModSecurity: APR compiled version="1.4.5"; loaded version="1.4.6" [Fri May 25 19:52:41 2012] [warn] ModSecurity: Loaded APR do not match with compiled! [Fri May 25 19:52:41 2012] [notice] ModSecurity: PCRE compiled version="8.12"; loaded version="8.12 2011-01-15" [Fri May 25 19:52:41 2012] [notice] ModSecurity: LUA compiled version="Lua 5.1" [Fri May 25 19:52:41 2012] [notice] ModSecurity: LIBXML compiled version="2.7.8" [Fri May 25 19:53:11 2012] [notice] ModSecurity for Apache/2.6.3 (http://www.modsecurity.org/) configured. [Fri May 25 19:53:11 2012] [notice] ModSecurity: APR compiled version="1.4.5"; loaded version="1.4.6" [Fri May 25 19:53:11 2012] [warn] ModSecurity: Loaded APR do not match with compiled! [Fri May 25 19:53:11 2012] [notice] ModSecurity: PCRE compiled version="8.12"; loaded version="8.12 2011-01-15" [Fri May 25 19:53:11 2012] [notice] ModSecurity: LUA compiled version="Lua 5.1" [Fri May 25 19:53:11 2012] [notice] ModSecurity: LIBXML compiled version="2.7.8" [Fri May 25 19:53:12 2012] [notice] Apache/2.2.22 (Ubuntu) PHP/5.3.8-ZS5.5.0 configured -- resuming normal operations and here is my httpd.conf: # Name based virtual hosting <virtualhost *:80> ServerName www-redirect KeepAlive Off RewriteEngine On RewriteCond %{HTTP_HOST} ^[^\./]+\.[^\./]+$ RewriteRule ^/(.*)$ http://www.%{HTTP_HOST}/$1 [R=301,L] </virtualhost> Alias /shared/js "/home/web/library/js" Alias /shared/image "/home/web/library/image" <IfModule mod_expires.c> <FilesMatch "\.(jpe?g|png|gif|js|css|doc|rtf|xls|pdf)$"> ExpiresActive On ExpiresDefault "access plus 1 week" </FilesMatch> </IfModule> ErrorLog ${APACHE_LOG_DIR}/error.log LogLevel warn <Directory /> Options FollowSymLinks AllowOverride None Order allow,deny allow from all </Directory> <Location /> RewriteEngine On RewriteCond %{REQUEST_FILENAME} -s [OR] RewriteCond %{REQUEST_FILENAME} -l [OR] RewriteCond %{REQUEST_FILENAME} -d RewriteRule ^.*$ - [NC,L] RewriteRule ^.*$ /index.php [NC,L] </Location> netstat -tap gives: Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 *:mysql *:* LISTEN 765/mysqld tcp 0 0 *:pop3 *:* LISTEN 744/dovecot tcp 0 0 *:imap2 *:* LISTEN 744/dovecot tcp 0 0 *:http *:* LISTEN 19861/apache2 tcp 0 0 *:smtp *:* LISTEN 30365/master tcp 0 0 *:4444 *:* LISTEN 634/sshd tcp 0 0 *:kamanda *:* LISTEN 1167/lighttpd tcp 0 0 *:imaps *:* LISTEN 744/dovecot tcp 0 0 *:amandaidx *:* LISTEN 1167/lighttpd tcp 0 0 localhost.loc:amidxtape *:* LISTEN 19861/apache2 tcp 0 0 *:pop3s *:* LISTEN 744/dovecot tcp 0 384 mail.mysite.:4444 231.214.14.37.dyn:41909 ESTABLISHED 19039/sshd: web [pr tcp 0 0 localhost.localdo:mysql localhost.localdo:48252 ESTABLISHED 765/mysqld tcp 0 0 mail.mysite.:http 231.214.14.37.dyn:54686 TIME_WAIT - tcp 0 0 mail.mysite.:4444 231.214.14.37.dyn:42419 ESTABLISHED 19372/sshd: web [pr tcp 0 0 localhost.localdo:48252 localhost.localdo:mysql ESTABLISHED 19884/auth tcp 0 0 mail.mysite.:http 231.214.14.37.dyn:54685 TIME_WAIT - tcp6 0 0 [::]:pop3 [::]:* LISTEN 744/dovecot tcp6 0 0 [::]:imap2 [::]:* LISTEN 744/dovecot tcp6 0 0 [::]:smtp [::]:* LISTEN 30365/master tcp6 0 0 [::]:4444 [::]:* LISTEN 634/sshd tcp6 0 0 [::]:imaps [::]:* LISTEN 744/dovecot tcp6 0 0 [::]:pop3s [::]:* LISTEN 744/dovecot Anyone knows what I am doing wrong? Perhaps I should take some additional steps to make apache listen 0n 443 but that it stops listening on 80 altogether I can't understand.

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• Simple Cisco ASA 5505 config issue

  - by Ben Sebborn

  I have a Cisco ASA setup with two interfaces: inside: 192.168.2.254 / 255.255.255.0 SecLevel:100 outside: 192.168.3.250 / 255.255.255.0 SecLevel: 0 I have a static route setup to allow PCs on the inside network to access the internet via a gateway on the outside interface (3.254): outside 0.0.0.0 0.0.0.0 192.168.3.254 This all works fine. I now need to be able to access a PC on the outside interface (3.253) from a PC on the inside interface on port 35300. I understand I should be able to do this with no problems, as I'm going from a higher security level to a lower one. However I can't get any connection. Do I need to set up a seperate static route? Perhaps the route above is overriding what I need to be able to do (is it routing ALL traffic through the gateway?) Any advice on how to do this would be apprecaited. I am configuring this via ASDM but the config can be seen as below: Result of the command: "show running-config" : Saved : ASA Version 8.2(5) ! hostname ciscoasa domain-name xxx.internal names name 192.168.2.201 dev.xxx.internal description Internal Dev server name 192.168.2.200 Newserver ! interface Ethernet0/0 switchport access vlan 2 ! interface Ethernet0/1 ! interface Ethernet0/2 ! interface Ethernet0/3 shutdown ! interface Ethernet0/4 shutdown ! interface Ethernet0/5 shutdown ! interface Ethernet0/6 shutdown ! interface Ethernet0/7 shutdown ! interface Vlan1 nameif inside security-level 100 ip address 192.168.2.254 255.255.255.0 ! interface Vlan2 nameif outside security-level 0 ip address 192.168.3.250 255.255.255.0 ! ! time-range Workingtime periodic weekdays 9:00 to 18:00 ! ftp mode passive clock timezone GMT/BST 0 clock summer-time GMT/BDT recurring last Sun Mar 1:00 last Sun Oct 2:00 dns domain-lookup inside dns server-group DefaultDNS name-server Newserver domain-name xxx.internal same-security-traffic permit inter-interface object-group service Mysql tcp port-object eq 3306 object-group protocol TCPUDP protocol-object udp protocol-object tcp access-list inside_access_in extended permit ip any any access-list outside_access_in remark ENABLES OUTSDIE ACCESS TO DEV SERVER! access-list outside_access_in extended permit tcp any interface outside eq www time-range Workingtime inactive access-list outside_access_in extended permit tcp host www-1.xxx.com interface outside eq ssh access-list inside_access_in_1 extended permit tcp any any eq www access-list inside_access_in_1 extended permit tcp any any eq https access-list inside_access_in_1 remark Connect to SSH services access-list inside_access_in_1 extended permit tcp any any eq ssh access-list inside_access_in_1 remark Connect to mysql server access-list inside_access_in_1 extended permit tcp any host mysql.xxx.com object-group Mysql access-list inside_access_in_1 extended permit tcp any host mysql.xxx.com eq 3312 access-list inside_access_in_1 extended permit object-group TCPUDP host Newserver any eq domain access-list inside_access_in_1 extended permit icmp any any access-list inside_access_in_1 remark Draytek Admin access-list inside_access_in_1 extended permit tcp any 192.168.3.0 255.255.255.0 eq 4433 access-list inside_access_in_1 remark Phone System access-list inside_access_in_1 extended permit tcp any 192.168.3.0 255.255.255.0 eq 35300 log disable pager lines 24 logging enable logging asdm warnings logging from-address [email protected] logging recipient-address [email protected] level errors mtu inside 1500 mtu outside 1500 ip verify reverse-path interface inside ip verify reverse-path interface outside ipv6 access-list inside_access_ipv6_in permit tcp any any eq www ipv6 access-list inside_access_ipv6_in permit tcp any any eq https ipv6 access-list inside_access_ipv6_in permit tcp any any eq ssh ipv6 access-list inside_access_ipv6_in permit icmp6 any any icmp unreachable rate-limit 1 burst-size 1 icmp permit any outside no asdm history enable arp timeout 14400 global (outside) 1 interface nat (inside) 1 0.0.0.0 0.0.0.0 static (inside,outside) tcp interface www dev.xxx.internal www netmask 255.255.255.255 static (inside,outside) tcp interface ssh dev.xxx.internal ssh netmask 255.255.255.255 access-group inside_access_in in interface inside control-plane access-group inside_access_in_1 in interface inside access-group inside_access_ipv6_in in interface inside access-group outside_access_in in interface outside route outside 0.0.0.0 0.0.0.0 192.168.3.254 10 route outside 192.168.3.252 255.255.255.255 192.168.3.252 1 timeout xlate 3:00:00 timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 icmp 0:00:02 timeout sunrpc 0:10:00 h323 0:05:00 h225 1:00:00 mgcp 0:05:00 mgcp-pat 0:05:00 timeout sip 0:30:00 sip_media 0:02:00 sip-invite 0:03:00 sip-disconnect 0:02:00 timeout sip-provisional-media 0:02:00 uauth 0:05:00 absolute timeout tcp-proxy-reassembly 0:01:00 timeout floating-conn 0:00:00 dynamic-access-policy-record DfltAccessPolicy aaa authentication telnet console LOCAL aaa authentication enable console LOCAL

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• how limit the number of open TCP streams from same IP to a local port?

  - by JMW

  Hi, i would like to limit the number of concurrent open TCP streams from the the same IP to the server's (local) port. Let's say 4 concurrent conncetions. How can this be done with ip tables? the closest thing, that i've found was: In Apache, is there a way to limit the number of new connections per second/hour/day? iptables -A INPUT -p tcp --dport 80 -i eth0 -m state --state NEW -m recent --set iptables -A INPUT -p tcp --dport 80 -i eth0 -m state --state NEW -m recent --update --seconds 86400 --hitcount 100 -j REJECT But this limitation just messures the number of new connections over the time. This might be good for controlling HTTP traffic. But this is not a good solution for me, since my TCP streams usually have a lifetime between 5 minutes and 2 hours. thanks a lot in advance for any reply :)

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• C# Sockets Buffer Overflow No Error

  - by Michael Covelli

  I have one thread that is receiving data over a socket like this: while (sock.Connected) { // Receive Data (Block if no data) recvn = sock.Receive(recvb, 0, rlen, SocketFlags.None, out serr); if (recvn <= 0 || sock == null || !sock.Connected) { OnError("Error In Receive, recvn <= 0 || sock == null || !sock.Connected"); return; } else if (serr != SocketError.Success) { OnError("Error In Receive, serr = " + serr); return; } // Copy Data Into Tokenizer tknz.Read(recvb, recvn); // Parse Data while (tknz.MoveToNext()) { try { ParseMessageAndRaiseEvents(tknz.Buffer(), tknz.Length); } catch (System.Exception ex) { string BadMessage = ByteArrayToStringClean(tknz.Buffer(), tknz.Length); string msg = string.Format("Exception in MDWrapper Parsing Message, Ex = {0}, Msg = {1}", ex.Message, BadMessage); OnError(msg); } } } And I kept seeing occasional errors in my parsing function indicating that the message wasn't valid. At first, I thought that my tokenizer class was broken. But after logging all the incoming bytes to the tokenizer, it turns out that the raw bytes in recvb weren't a valid message. I didn't think that corrupted data like this was possible with a tcp data stream. I figured it had to be some type of buffer overflow so I set sock.ReceiveBufferSize = 1024 * 1024 * 8; and the parsing error never, ever occurs in testing (it happens often enough to replicate if I don't change the ReceiveBufferSize). But my question is: why wasn't I seeing an exception or an error state or something if the socket's internal buffer was overflowing before I changed this buffer size?

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• Elmah for non-HTTP protocol applications OR Elmah without HttpContext

  - by Josh

  We are working on a 3-tier application, and we've been allowed to use the latest and greatest (MVC2, IIS7.5, WCF, SQL2k8, etc). The application tier is exposed to the various web applications by WCF services. Since we control both the service and client side, we've decided to use net.tcp bindings for their performance advantage over HTTP. We would like to use ELMAH for the error logging, both on the web apps and services. Here's my question. There's lots of information about using ELMAH with WCF, but it is all for HTTP bindings. Does anyone know if/how you can use ELMAH with WCF services exposing non-HTTP endpoints? My guess is no, because ELMAH wants the HttpContext, which requires the AspNetCompatibilityEnabled flag to be true in the web.config. From MSDN: IIS 7.0 and WAS allows WCF services to communicate over protocols other than HTTP. However, WCF services running in applications that have enabled ASP.NET compatibility mode are not permitted to expose non-HTTP endpoints. Such a configuration generates an activation exception when the service receives its first message. If it is true that you cannot use ELMAH with WCF services having non-HTTP endpoints, then the follow-up question is: Can we use ELMAH in such a way that doesn't need HttpContext? Or more generally (so as not to commit the thin metal ruler error), is there ANY way to use ELMAH with WCF services having non-HTTP endpoints?

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• .NET Sockets Buffer Overflow No Error

  - by Michael Covelli

  I have one thread that is receiving data over a socket like this: while (sock.Connected) { // Receive Data (Block if no data) recvn = sock.Receive(recvb, 0, rlen, SocketFlags.None, out serr); if (recvn <= 0 || sock == null || !sock.Connected) { OnError("Error In Receive, recvn <= 0 || sock == null || !sock.Connected"); return; } else if (serr != SocketError.Success) { OnError("Error In Receive, serr = " + serr); return; } // Copy Data Into Tokenizer tknz.Read(recvb, recvn); // Parse Data while (tknz.MoveToNext()) { try { ParseMessageAndRaiseEvents(tknz.Buffer(), tknz.Length); } catch (System.Exception ex) { string BadMessage = ByteArrayToStringClean(tknz.Buffer(), tknz.Length); string msg = string.Format("Exception in MDWrapper Parsing Message, Ex = {0}, Msg = {1}", ex.Message, BadMessage); OnError(msg); } } } And I kept seeing occasional errors in my parsing function indicating that the message wasn't valid. At first, I thought that my tokenizer class was broken. But after logging all the incoming bytes to the tokenizer, it turns out that the raw bytes in recvb weren't a valid message. I didn't think that corrupted data like this was possible with a tcp data stream. I figured it had to be some type of buffer overflow so I set sock.ReceiveBufferSize = 1024 * 1024 * 8; and the parsing error never, ever occurs in testing (it happens often enough to replicate if I don't change the ReceiveBufferSize). But my question is: why wasn't I seeing an exception or an error state or something if the socket's internal buffer was overflowing before I changed this buffer size?

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