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• Custom SQL Server driver

  - by hoodoos

  I had a crazy thought about writing my own SQL Server driver to make it work something like non-blocking http client, so it won't be thread thirsty and could handle lots of db queries within one thread. I tried to look over google for some guidelines about implementing SQL Server client protocol, but found none really, where do those guys get information about it when they write own implementations for PHP or python? I need a really low level to be documented so I can implement all phases of working with a connection through sockets. And would be really nice to have a an example in c# language. :)

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• Auto enter pass phrase in case of Python ssl Client/Server

  - by rauch

  I need to create Client/Server application to send files from clients to Server. I use simple ssl sockets for that and authenticate with certificates. ms = socket.socket(socket.AF_INET, socket.SOCK_STREAM) ssl_sock = ssl.wrap_socket(ms, keyfile=".../newCA/my_client.key", certfile=".../newCA/my_client.crt", server_side=0, cert_reqs=ssl.CERT_REQUIRED, ca_certs=".../newCA/CA/my-ca.crt" ) ssl_sock.connect((HOST, MPORT)) And Server side: msock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) self.ssl_sock = ssl.wrap_socket(msock, keyfile=".../newCA/my_server.key", certfile=".../newCA/my_server.crt", server_side=1, cert_reqs=ssl.CERT_REQUIRED, ca_certs=".../newCA/CA/my-ca.crt" ) self.ssl_sock.bind(('', self.PORT)) self.ssl_sock.listen(self.QUEUE_MAX) The problem is the following: when client tries to connect to Server, it requires Enter the pass phrase for private key for Both: for Server-side and Client-side. In Java we need to set System Property: javax.net.ssl.keyStorePassword="" and it has to be used automatically, But how is it been used in Python? I can't enter pass phrase all time the client connects.

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• How to create an adhoc network between laptops in java?

  - by Muaz

  Hello, I want to create an adhoc between labtops were they will communicate using wireless communication. I will use java for this but still I do not know how to start.. I think I'll have to use sockets for the connections right? How will a laptop notice other laptops in its local network or the other way around? Do i need a server to handle the communication between laptops? Another thing, how to broadcast a message from one laptop to other laptops in the network? Please reply as soon as you can. Any help will be appreciated. Thanks in advance.

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• How to test for secure SMTP mail service on a mail server

  - by Vinay S Shenoy

  I'm working on a project to auto-configure a user's email server settings in Java. I am extracting the mail server from his email address and looking up the MX records of that mail server using the DirContext class with com.sun.jndi.dns.DnsContextFactory. Then I'm opening a Socket to each server and testing them using a HELO command and checking the responses. My problem is that this works only when I test it with the unsecure SMTP port 25. How can I use it with the secure port 465? I tried using Secure Sockets by using SSLSocketFactory sslsocketfactory = (SSLSocketFactory)SSLSocketFactory.getDefault(); SSLSocket socket = (SSLSocket)sslsocketfactory.createSocket(mailserver, STANDARD_SMTP_PORT); But all connections get a timeout exception as follows alt1.gmail-smtp-in.l.google.com. java.net.ConnectException: Operation timed out Please help.

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• Struct sockaddr, sin_family is not a member

  - by leon22

  According to this article from msdn ( http://msdn.microsoft.com/en-us/library/windows/desktop/ms740496(v=vs.85).aspx) the struct varies depending on which protocol is selected! Now I want to use this code from http://www.intelliproject.net/articles/showArticle/index/check_tcp_udp_port to check if a port is open or not! Now I have the struct sockaddr as follows: struct sockaddr { ushort sa_family; char sa_data[14]; }; but need this strcuture: struct sockaddr { short sin_family; u_short sin_port; struct in_addr sin_addr; char sin_zero[8]; }; Which changes are necessary? (Ws2_32.lib is linked and following includes #define WIN32_LEAN_AND_MEAN // sockets #include "windows.h" #include <winsock2.h> #include <ws2tcpip.h> Thx

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• How to receive HTTP messages using Socket

  - by Poma

  I'm using Socket class for my web client. I can't use HttpWebRequest since it doesn't support socks proxies. So I have to parse headers and handle chunked encoding by myself. The most difficult thing is to determine length of content so I have to read it byte-by-byte. First I have to use ReadByte() to find last header ("\r\n\r\n" combination), then read chunk's size etc. But this approach has very poor performance. Can you suggest better solution? Maybe some open source examples or libraries that handle http request through sockets (not very big and complicated though, I'm a noob)

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• Is a Service Bus a good option to communicate with multiple external servers?

  - by PFreitas

  We are developing an application that communicates, via web services or TCP/IP sockets, with multiple servers (up to 50 different external companies). Basically, the exchanged messages are the same (XML), but depending on the inputs of our application we should call 1 or more external servers. The benefits we would expect of introducing a Service Bus in the architecture would be: 1- Remove the need to manage all point-to-point configurations (all the 50 endpoints); 2- Simplify the communication layer of our application by having only one server to talk to; Is a Service Bus a good architectural option for this scenario? What is the best (simplest) Service Bus for this kind of communication? I read a few MSDN articles on Azure Service Bus Relay, but it didn’t seem to fit our needs. Am I wrong? Thanks for your help.

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• Creating TCP network errors for unit testing

  - by Robert S. Barnes

  I'd like to create various network errors during testing. I'm using the Berkely sockets API directly in C++ on Linux. I'm running a mock server in another thread from within Boost.Test which listens on localhost. For instance, I'd like to create a timeout during connect. So far I've tried not calling accept in my mock server and setting the backlog to 1, then making multiple connections, but all seem to successfully connect. I would think that if there wasn't room in the backlog queue I would at least get a connection refused error if not a timeout. I'd like to do this all programatically if possible, but I'd consider using something external like IPchains to intentionally drop certain packets to certain ports during testing, but I'd need to automate creating and removing rules so I could do it from within my Boost.Test unit tests. I suppose I could mock the various system calls involved, but I'd rather go through a real TCP stack if possible. Ideas?

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• I have a ConnectException that isn't being caught for some reason

  - by aakbari1024

  I'm working on an Android application that uses sockets. I have a function called initializeStreams() which opens the socket and attempts a connection. This function throws a ConnectException if the connection could not be established. But for some reason, in the code that calls initializeStreams(), which has a catch block for ConnectException, the log prints out its own stack trace for the exception instead of going to the catch block. The catch block is never reached at all, even though the exact exception is being thrown. Here's the code: The try block: try { initializeStreams(); /* drivesList = new ArrayList<String>(); drivesList = enumerateDrives();*/ } catch (ConnectException e) { //Log.i(TAG, "caught connect exception"); /*loadingProgress.dismiss(); retryConnection();*/ } initializeStreams(): public void initializeStreams() throws ConnectException { try { Log.i(TAG, "Attempting to connect"); requestSocket = new Socket(SERVER_ADDR, PORT); /* other code */ } catch (IOException e) { e.printStackTrace(); } I can't figure this out, so any help would be much appreciated. }

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• Network programming on java

  - by maks

  I have written a simple network program on java using sockets. Program has a client and a server. When user types a word on client side, server simply return this word to client. On server side I use Serversocket and bind it to port 4444. Why does not firewall block this connection on my server PC? I ask this question because earlier I wrote this program using corba technology, and firewall on my server PC was blocking the connection to this port; when I disabled the firewall the program worked fine.

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• Sending a large file over network continuously

  - by David Parunakian

  Hello, We need to write software that would continuously (i.e. new data is sent as it becomes available) send very large files (several Tb) to several destinations simultaneously. Some destinations have a dedicated fiber connection to the source, while some do not. Several questions arise: We plan to use TCP sockets for this task. What failover procedure would you recommend in order to handle network outages and dropped connections? What should happen upon upload completion: should the server close the socket? If so, then is it a good design decision to have another daemon provide file checksums on another port? Could you recommend a method to handle corrupted files, aside from downloading them again? Perhaps I could break them into 10Mb chunks and calculate checksums for each chunk separately? Thanks.

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• How to read from port#### on home IP 127.0.0.1 [SOLVED]

  - by Ree

  I have a program that sends data to the home IP to the port####. I want to access this and make it readable data. Maybe in C#? I haven't tried doing this before and I have only a vague idea of doing sockets. Any ideas as to how I can manage this? Thanks - Ree EDIT The program I'm trying access is a UDP. Therefore it's a UDP port reader I need to incorporate on another program. "####" < is just any random number. SOLUTION: http://msdn.microsoft.com/en-us/library/tst0kwb1.aspx

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• Stocket server crashing with unhandled exception

  - by Rob

  We have a c# (3.5 framework) socket server which is a console app, after about 3000 connections (or less, it's quite random), we get an unhandled exception which crashes the app completely. We're really struggling to find out what's happening and where, the only info we get is below, can anyone shed any light? It should be noted that EVERYTHING is wrapped up in try catch{} Description: Stopped working Problem signature: Problem Event Name: CLR20r3 Problem Signature 01: qrushrserver.exe Problem Signature 02: 1.0.0.0 Problem Signature 03: 4bf56a0c Problem Signature 04: System Problem Signature 05: 2.0.0.0 Problem Signature 06: 49cc5ec9 Problem Signature 07: 2c0b Problem Signature 08: 40 Problem Signature 09: System.Net.Sockets.Socket OS Version: 6.0.6002.2.2.0.1296.17 Locale ID: 2057 Faulting application app_name.exe, version 1.0.0.0, time stamp 0x4bf56a0c, faulting module mscorwks.dll, version 2.0.50727.4200, time stamp 0x4a9ee32d, exception code 0xc0000005, fault offset 0x00000000001c89ca, process id 0x%9, application start time 0x%10. .NET Runtime version 2.0.50727.4200 - Fatal Execution Engine Error (000007FEF8E4664E) (80131506)

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• How to empty a socket in python?

  - by luc

  I need to empty the data on a socket (making sure that there is nothing to receive). Unfortunately, there is no function for this in the python socket module. I've implemented something this way: def empty_socket(sock): """remove the data present on the socket""" input = [sock] while 1: inputready, o, e = select.select(input,[],[], 0.0) if len(inputready)==0: break for s in inputready: s.recv(1) What do you think? Is there a better way to do that? Update: I don't want to change the socket timeout. What's why i prefer a select to a read. Update: The original question was using the 'flush' term. It seems that 'empty' is a better term. Update - 2010-02-27 : I've noticed a bug after when the pair has closed. The inputready is always filled with the sockets. I fixed that by adding a maximum number of loops. Is there a better fix?

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• Send data over telnet without pressing enter

  - by Matt

  I've recently started messing around with Java sockets and telnet... I want the user to be able to connect to the server, just type a letter and have it sent to the server, without pressing enter to send it. I'm sure there's no way for the server to set this up, but maybe telnet has a parameter or something which could allow this? Maybe if I got the user to type stty cbreak or stty raw before running telnet, this would work? (UNIX only, I know!) If I can get telnet to do this then it saves me having to write a special client just for this feature...

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• Find original owning process of a Linux socket

  - by Rob H

  In Linux and other UNIX-like operating systems, it is possible for two (or more) processes to share an Internet socket. Assuming there is no parent-child relationship between the processes, is there any way to tell what process originally created a socket? Clarification: I need to determine this from "outside" the processes using the /proc filesystem or similar. I can't modify the code of the processes. I can already tell what processes are sharing sockets by reading /proc/<pid>/fd, but that doesn't tell me what process originally created them.

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• Socket c# not listen on port over internet?

  - by Nguy?n Van Th?ng

  Code server I have server listen on port 1450: //Using UDP sockets clientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp); EndPoint ourEP = new IPEndPoint(IPAddress.Any, 1450); //Listen asynchronously on port 1450 for coming messages (Invite, Bye, etc). clientSocket.Bind(ourEP); //Receive data from any IP. EndPoint remoteEP = (EndPoint)(new IPEndPoint(IPAddress.Any, 0)); byteData = new byte[1024]; //Receive data asynchornously. clientSocket.BeginReceiveFrom(byteData, 0, byteData.Length, SocketFlags.None, ref remoteEP, new AsyncCallback(OnReceive), null); but code on not open port 1450 and client connect: otherPartyIP = new IPEndPoint(IPAddress.Parse(txtCallToIP.Text), 1450); otherPartyEP = (EndPoint)otherPartyIP; When i run code client and server in lan network it's ok. but run over network i check port 1450 in lan not open. tell me how open port 1450 in code server? thanks

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• conditional beginReceive

  - by sbenderli

  I am writing a client program that uses Sockets. I would like the client to receive asyncronously UNLESS it is expecting a response, in which case I would like to receive syncronously. My current problem is that because I have to make a call to socket.BeginReceive which waits until there's data on the buffer, the async call always happens prior to the sync call.. How could I temporarily stop BeginReceive from executing? Is there a way to call EndReceive and then once I am done receiving syncronously, I can continue to receive asnycronously?

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• SYN receives RST,ACK very frequently

  - by user1289508

  Hi Socket Programming experts, I am writing a proxy server on Linux for SQL Database server running on Windows. The proxy is coded using bsd sockets and in C, and it is working just fine. When I use a database client (written in JAVA, and running on a Linux box) to fire queries (with a concurrency of 100 or more) directly to the Database server, not experiencing connection resets. But through my proxy I am experiencing many connection resets. Digging deeper I came to know that connection from 'DB client' to 'Proxy' always succeeds but when the 'Proxy' tries to connect to the DB server the connection fails, due to the SYN packet getting RST,ACK. That was to give some background. The question is : Why does sometimes SYN receives RST,ACK? 'DB client(linux)' to 'Server(windows)' ---- Works fine 'DB client(linux) to 'Proxy(Linux)' to 'Server(windows)' ----- problematic I am aware that this can happen in "connection refused" case but this definitely is not that one. SYN flooding might be another scenario, but that does not explain fine behavior while firing to Server directly. I am suspecting some socket option setting may be required, that the client does before connecting and my proxy does not. Please put some light on this. Any help (links or pointers) is most appreciated. Additional info: Wrote a C client that does concurrent connections, which takes concurrency as an argument. Here are my observations: - At 5000 concurrency and above, some connects failed with 'connection refused'. - Below 2000, it works fine. But the actual problem is observed even at a concurrency of 100 or more. Note: The problem is time dependent sometimes it never comes at all and sometimes it is very frequent and DB client (directly to server) works fine at all times .

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• How can I limit the number of open AF_INET sockets?

  - by Stefano Palazzo

  Is there a way to limit the number of concurretly open AF_INET sockets (only)? If so, how do I do it, and how will the networking behave if I'm above the limit? For background: My cheap commodity router is a bit eager to detect 'syn flooding'. When it does, it crashes (and doesn't automatically restart itself). I'm thinking limiting concurrent connections to around 1000 should keep it from bickering.

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• Server socket programming in Android 1.5, most power efficient way?

  - by Antek

  Hello people, I am doing a project where I have too develop an application that listens for incoming events by a service. The device that has to listen too events is an Android phone with Android SDK 1.5 on it. Currently the services that call events only implement communication trough UDP or TCP sockets. I can solve my problem by setting up a ServerSocket, but i doubt that's the most power efficient way. This application will be running most of the time, with Wi-Fi on, and I'd like too reach an long battery duration. I've been looking for options on the internet for my question for a while but i couldn't get a real answer. I've got the following questions: What is the most efficient way too listen to incoming events? Should I make an ServerSocket? or what are my options? Are there any other implementations that are more power efficient? Ive been also thinking of implementing communication trough XMPP. Not sure if this is the best way. I'm not forced too an specific implementation. All suggestions are welcome! Thanks for the help, Antek

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• Poco SocketReactors for a Proxy Server

  - by Genesis

  Can anyone give me some idea of the best way to implement a non-blocking proxy server using a Poco Socket Reactor? Currently I have a blocking implementation where if a readable notification arrives from the client I am writing what is read directly to the server, and if a readable notification arrives from the server I am writing what is read directly to the client. To achieve this I keep the thread that initiated the server connection alive but I would prefer to switch to non-blocking and have any threads which are used to initiate a connection removed once the server and client sockets are registered with the reactor and the SOCKS5 handshake is over. With a SocketReactor one can register event handlers for a single socket but the trouble is I would need to store whatever is read from that socket in a global buffer until the corresponding server socket is ready to be written to as from my testing I dont seem to be able to just write directly to the server when client data arrives. I am thinking of using a struct that contains the client socket, server socket, client buffer and server buffer and whenever a writable notification comes along for either the client or server, finding the corresponding buffer and writing this. Any thoughts?

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• Nonblocking Tcp server

  - by hoodoos

  It's not a question really, i'm just looking for some guidelines :) I'm currently writing some abstract tcp server which should use as low number of threads as it can. Currently it works this way. I have a thread doing listening and some worker threads. Listener thread is just sits and wait for clients to connect I expect to have a single listener thread per server instance. Worker threads are doing all read/write/processing job on clients socket. So my problem is in building efficient worker process. And I came to some problem I can't really solve yet. Worker code is something like that(code is really simple just to show a place where i have my problem): List<Socket> readSockets = new List<Socket>(); List<Socket> writeSockets = new List<Socket>(); List<Socket> errorSockets = new List<Socket>(); while( true ){ Socket.Select( readSockets, writeSockets, errorSockets, 10 ); foreach( readSocket in readSockets ){ // do reading here } foreach( writeSocket in writeSockets ){ // do writing here } // POINT2 and here's the problem i will describe below } it works all smothly accept for 100% CPU utilization because of while loop being cycling all over again, if I have my clients doing send-receive-disconnect routine it's not that painful, but if I try to keep alive doing send-receive-send-receive all over again it really eats up all CPU. So my first idea was to put a sleep there, I check if all sockets have their data send and then putting Thread.Sleep in POINT2 just for 10ms, but this 10ms later on produces a huge delay of that 10ms when I want to receive next command from client socket.. For example if I don't try to "keep alive" commands are being executed within 10-15ms and with keep alive it becomes worse by atleast 10ms :( Maybe it's just a poor architecture? What can be done so my processor won't get 100% utilization and my server to react on something appear in client socket as soon as possible? Maybe somebody can point a good example of nonblocking server and architecture it should maintain?

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• Make Python Socket Server More Efficient

  - by BenMills

  I have very little experience working with sockets and multithreaded programming so to learn more I decided to see if I could hack together a little python socket server to power a chat room. I ended up getting it working pretty well but then I noticed my server's CPU usage spiked up over 100% when I had it running in the background. Here is my code in full: http://gist.github.com/332132 I know this is a pretty open ended question so besides just helping with my code are there any good articles I could read that could help me learn more about this? My full code: import select import socket import sys import threading from daemon import Daemon class Server: def __init__(self): self.host = '' self.port = 9998 self.backlog = 5 self.size = 1024 self.server = None self.threads = [] self.send_count = 0 def open_socket(self): try: self.server = socket.socket(socket.AF_INET6, socket.SOCK_STREAM) self.server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) self.server.bind((self.host,self.port)) self.server.listen(5) print "Server Started..." except socket.error, (value,message): if self.server: self.server.close() print "Could not open socket: " + message sys.exit(1) def remove_thread(self, t): t.join() def send_to_children(self, msg): self.send_count = 0 for t in self.threads: t.send_msg(msg) print 'Sent to '+str(self.send_count)+" of "+str(len(self.threads)) def run(self): self.open_socket() input = [self.server,sys.stdin] running = 1 while running: inputready,outputready,exceptready = select.select(input,[],[]) for s in inputready: if s == self.server: # handle the server socket c = Client(self.server.accept(), self) c.start() self.threads.append(c) print "Num of clients: "+str(len(self.threads)) self.server.close() for c in self.threads: c.join() class Client(threading.Thread): def __init__(self,(client,address), server): threading.Thread.__init__(self) self.client = client self.address = address self.size = 1024 self.server = server self.running = True def send_msg(self, msg): if self.running: self.client.send(msg) self.server.send_count += 1 def run(self): while self.running: data = self.client.recv(self.size) if data: print data self.server.send_to_children(data) else: self.running = False self.server.threads.remove(self) self.client.close() """ Run Server """ class DaemonServer(Daemon): def run(self): s = Server() s.run() if __name__ == "__main__": d = DaemonServer('/var/servers/fserver.pid') if len(sys.argv) == 2: if 'start' == sys.argv[1]: d.start() elif 'stop' == sys.argv[1]: d.stop() elif 'restart' == sys.argv[1]: d.restart() else: print "Unknown command" sys.exit(2) sys.exit(0) else: print "usage: %s start|stop|restart" % sys.argv[0] sys.exit(2)

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• why does text from socket server erase previously written text?

  - by mix

  This is strange enough I'm not sure how to search for an answer. I have a program in Python that communicates via TCP/IP sockets to a telnet-based server. If I telnet in manually and type commands like this: SET MDI G0 X0 Y0 the server will spit back a line like this: SET MDI ACK Pretty standard stuff. Here's the weird part. If, in my code, I precede my printing of each of these lines with some text, the returned line erases what I'm trying to print before it. So for example, if I write the code so it should look like this: SENT: SET MDI G0 X0 Y0 READ: SET MDI ACK What I get instead is: SENT: SET MDI G0 X0 Y0 SET MDI ACK Now, if I make the "READ: " text a bit longer, I can get a better idea of what's happening. Let's say I change READ: to 12345678901234567890, so that it should read as: 12345678901234567890: SET MDI ACK What I get instead is: SET MDI ACK234567890: So it seems like whatever text I'm getting back from the server is somehow deleting what I'm trying to precede it with. I tried saving all of my saved lines in a list, and then printing them out at the end, but it does exactly the same thing. Any ideas on what's going on, or even on how to debug this? Is there a way to get Python to show me any hidden chars in a string, for example? thx!

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