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• Android bluetooth socket error

  - by ashwini

  I am using backport bluetooth api on android 1.6. I am using Google Bluetooth Chat sample app for testing. The app works fine in normal scenarios. In a scenario, when I try to connect to paired device which is in off state, I get following error. 01-04 09:00:11.629: ERROR/BluetoothEventLoop.cpp(84): onGetRemoteServiceChannelResult: D-Bus error: org.bluez.Error.ConnectionAttemptFailed (Host is down) 01-04 09:00:11.729: DEBUG/dalvikvm(128): GC freed 4535 objects / 256008 bytes in 296ms 01-04 09:00:21.880: ERROR/bluetooth_RfcommSocket.cpp(1433): connect error: Host is down (112) But it sets the state as connected. The app is unable to catch the exception. Why does it happen? Or is it the case with backport api? Any help is appreciated as I am struggling a lot to get things run fine.

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• Buffer management for socket application best practice

  - by Poni

  Having a Windows IOCP app............ I understand that for async i/o operation (on network) the buffer must remain valid for the duration of the send/read operation. So for each connection I have one buffer for the reading. For sending I use buffers to which I copy the data to be sent. When the sending operation completes I release the buffer so it can be reused. So far it's nice and not of a big issue. What remains unclear is how do you guys do this? Another thing is that even when having things this way, I mean multi-buffers, the receiver side might be flooded (talking from experience) with data. Even setting SO_RCVBUF to 25MB didn't help in my testings. So what should I do? Have a to-be-sent queue?

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• method to find my UDP socket's "real" port?

  - by yairchu

  Is there any free service to which I could send a UDP packet and it would respond telling me what is my "real" UDP port? (my application is behind a NAT) This kind of service could allow me to make a p2p coordination server with normal php hosting. The p2p clients would know their UDP ports from this service They will then contact my server over HTTP (which is what regular web hosting allows) and tell it their port (and ip, which is normally supplied to cgi scripts) My server will give the clients the IP addresses and ports of the other clients.

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• Detecting I/O errors in a NON BLOCKING SOCKET

  - by ripunjay-tripathi-gmail-com

  I am writing a client - server system in which I used NON-BLOCKING sockets. My problem is to detect error { while performing send() or write() } that may occur while data transfer. Example lets say, while the data is being transferred the peer crashes. Another case there is some network problem, something like wire unplugged etc. As of now, I am using a high level ACK, that peer sends after receiving the complete data. Ripunjay Tripathi

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• C socket programming: client send() but server select() doesn't see it

  - by Fantastic Fourier

  Hey all, I have a server and a client running on two different machines where the client send()s but the server doesn't seem to receive the message. The server employs select() to monitor sockets for any incoming connections/messages. I can see that when the server accepts a new connection, it updates the fd_set array but always returns 0 despite the client send() messages. The connection is TCP and the machines are separated by like one router so dropping packets are highly unlikely. I have a feeling that it's not select() but perhaps send()/sendto() from client that may be the problem but I'm not sure how to go about localizing the problem area. while(1) { readset = info->read_set; ready = select(info->max_fd+1, &readset, NULL, NULL, &timeout); } above is the server side code where the server has a thread that runs select() indefinitely. rv = connect(sockfd, (struct sockaddr *) &server_address, sizeof(server_address)); printf("rv = %i\n", rv); if (rv < 0) { printf("MAIN: ERROR connect() %i: %s\n", errno, strerror(errno)); exit(1); } else printf("connected\n"); sleep(3); char * somemsg = "is this working yet?\0"; rv = send(sockfd, somemsg, sizeof(somemsg), NULL); if (rv < 0) printf("MAIN: ERROR send() %i: %s\n", errno, strerror(errno)); printf("MAIN: rv is %i\n", rv); rv = sendto(sockfd, somemsg, sizeof(somemsg), NULL, &server_address, sizeof(server_address)); if (rv < 0) printf("MAIN: ERROR sendto() %i: %s\n", errno, strerror(errno)); printf("MAIN: rv is %i\n", rv); and this is the client side where it connects and sends messages and returns connected MAIN: rv is 4 MAIN: rv is 4 any comments or insightful insights are appreciated.

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• Boost Asio UDP retrieve last packet in socket buffer

  - by Alberto Toglia

  I have been messing around Boost Asio for some days now but I got stuck with this weird behavior. Please let me explain. Computer A is sending continuos udp packets every 500 ms to computer B, computer B desires to read A's packets with it own velocity but only wants A's last packet, obviously the most updated one. It has come to my attention that when I do a: mSocket.receive_from(boost::asio::buffer(mBuffer), mEndPoint); I can get OLD packets that were not processed (almost everytime). Does this make any sense? A friend of mine told me that sockets maintain a buffer of packets and therefore If I read with a lower frequency than the sender this could happen. ¡? So, the first question is how is it possible to receive the last packet and discard the ones I missed? Later I tried using the async example of the Boost documentation but found it did not do what I wanted. http://www.boost.org/doc/libs/1_36_0/doc/html/boost_asio/tutorial/tutdaytime6.html From what I could tell the async_receive_from should call the method "handle_receive" when a packet arrives, and that works for the first packet after the service was "run". If I wanted to keep listening the port I should call the async_receive_from again in the handle code. right? BUT what I found is that I start an infinite loop, it doesn't wait till the next packet, it just enters "handle_receive" again and again. I'm not doing a server application, a lot of things are going on (its a game), so my second question is, do I have to use threads to use the async receive method properly, is there some example with threads and async receive? Thanks for you attention.

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• buffer size for socket connection in c++

  - by wyatt

  I'm trying to build a basic POP3 mail client in C/++, but I've run into a bit of an issue. Since you have to define the buffer size when building the program, but a message can be arbitrarily large, how do you, say, get the mail server to send it to you in parts? And if this isn't the correct means of solving the problem, what is? And while I'm here, can anyone confirm for me that RFC 2822 is still the current document defining email layout? Thanks

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• socket programming: How do I handle out of band data

  - by soulmerge

  I just looked into wikipedia's entry on out-of-band data and as far as I understand, OOB data is somehow flagged more important and treated as ordinary data, but transmitted in a seperate stream, which profoundly confuses me. The actual question would be (besides "Could someone explain what OOB data is?"): I'm writing a unix application that uses sockets and need to make use of select() and was wondering what to do with the exceptfds parameter? Do I need to put all my sockets into this parameter and react to such events? Or do I just ignore them?

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• How to deal with MySQL Connector/ODBC error "Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock'"

  - by user12653020

  I am sure many users run into a mysterious problem when perfectly working ODBC configurations started failing with errors like: Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' The above error message might be preceded with something like [nxDc[yQ]. At the same time odbc.ini specifies in its DSN different SOCKET=/tmp/mysql.sock or a TCP connection SERVER=<remote_host_or_ip>. The question is, what had happened that the ODBC driver started to ignore the DSN options? The clue lies in the corrupted string [nxDc[yQ], which actually was [UnixODBC][MySQL] with each 2nd symbol removed. This is the case of bad conversion from SQLCHAR to SQLWCHAR. The UnixODBC driver manager took a single-byte character string from the client application and tried to convert it into the wide (multi-byte) characters for the Unicode version of MyODBC driver: Initially the piece of the connection string was represented by 1-byte chars like: [S][E][R][V][E][R][=][m][y][h][o][s][t][;] after the bad conversion to wide chars (commonly 2-byte UTF-16) [SE][RV][ER][=m][yh][os][t;] instead of [S\0][E\0][R\0][V\0][E\0][R\0][=\0][m\0][y\0][h\0][o\0][s\0][t\0][;\0] Naturally, the MyODBC driver could not parse the bad string and tried to use the default connection type (SOCKET) with the default value (/var/lib/mysql/mysql.sock) Now we know what happened, but why it happened? In most cases it happened because of using ODBCManageDataSourcesQ4 utility or its older analog ODBCConfig. When registering ODBC drivers they put lots of additional options and one of these options badly affects the UnixODBC driver manager itself. The solution is simple - remove or comment out the option in odbcinst.ini file (it is empty by default) set for the driver: [MySQL ODBC 5.2.6 Driver] Description    = Driver         = /home/dbs/myodbc526/lib/libmyodbc5w.so Driver64       = /home/dbs/myodbc526/lib/libmyodbc5w.so Setup          = /home/dbs/myodbc526/lib/libmyodbc5S.so Setup64        = /home/dbs/myodbc526/lib/libmyodbc5S.so UsageCount     = 1 CPTimeout      = 0 CPTimeToLive   = 0 IconvEncoding  =  # <--------- remove this line Trace          = TraceFile      = TraceLibrary   = After applying this simple solution (remove the line with IconvEncoding = ) everything came to normal. Prior to removing that line I tried putting different encoding names there, but the result was not good, so I really don't know how to properly use it. Unfortunately, UnixODBC manuals say nothing about it. Therefore, removing this option was the only way to get things done.

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• breaking out from socket select

  - by kamziro

  I have a loop which basically calls this every few seconds (after the timeout): while(true){ if(finished) return; switch(select(FD_SETSIZE, &readfds, 0, 0, &tv)){ case SOCKET_ERROR : report bad stuff etc; return; default : break; } // do stuff with the incoming connection } So basically for every few seconds (which is specified by tv), it reactivates the listening. This is run on thread B (not a main thread). There are times when I want to end this acceptor loop immediately from thread A (main thread), but seems like I have to wait until the time interval finishes.. Is there a way to disrupt the select function from another thread so thread B can quit instantly?

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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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• How do I detect server status in a port scanner java implementation

  - by akz

  I am writing a port scanner in Java and I want to be able to distinct the following 4 use cases: port is open port is open and server banner was read port is closed server is not live I have the following code: InetAddress address = InetAddress.getByName("google.com"); int[] ports = new int[]{21, 22, 23, 80, 443}; for (int i = 0; i < ports.length; i++) { int port = ports[i]; Socket socket = null; try { socket = new Socket(address, port); socket.setSoTimeout(500); System.out.println("port " + port + " open"); BufferedReader reader = new BufferedReader( new InputStreamReader(socket.getInputStream())); String line = reader.readLine(); if (line != null) { System.out.println(line); } socket.close(); } catch (SocketTimeoutException ex) { // port was open but nothing was read from input stream ex.printStackTrace(); } catch (ConnectException ex) { // port is closed ex.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { if (socket != null && !socket.isClosed()) { try { socket.close(); } catch (Exception e) { e.printStackTrace(); } } } } The problem is that I get a ConnectionException both when the port is closed and the server cannot be reached but with a different exception message: java.net.ConnectException: Connection timed out: connect when the connection was never established and java.net.ConnectException: Connection refused: connect when the port was closed so I cannot make the distinction between the two use cases without digging into the actual exception message. Same thing happens when I try a different approach for the socket creation. If I use: socket = new Socket(); socket.setSoTimeout(500); socket.connect(new InetSocketAddress(address, port), 1000); I have the same problem but with the SocketTimeoutException instead. I get a java.net.SocketTimeoutException: Read timed out if port was open but there was no banner to be read and java.net.SocketTimeoutException: connect timed out if server is not live or port is closed. Any ideas? Thanks in advance!

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• XML RPC client for C# over secured socket (https)

  - by Ummar

  I have a secured (https) XML-RPC server written in python, and I have tested it with a python based client. but I need a C# based client for it, I have given a try to xml-rpc.net but it is not working with https? can any one please help me out? or I will have to write a client from scratch? Thanks

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• programs hangs during socket interaction

  - by herrturtur

  I have two programs, sendfile.py and recvfile.py that are supposed to interact to send a file across the network. They communicate over TCP sockets. The communication is supposed to go something like this: sender =====filename=====> receiver sender <===== 'ok' ======= receiver or sender <===== 'no' ======= receiver if ok: sender ====== file ======> receiver I've got The sender and receiver code is here: Sender: import sys from jmm_sockets import * if len(sys.argv) != 4: print "Usage:", sys.argv[0], "<host> <port> <filename>" sys.exit(1) s = getClientSocket(sys.argv[1], int(sys.argv[2])) try: f = open(sys.argv[3]) except IOError, msg: print "couldn't open file" sys.exit(1) # send filename s.send(sys.argv[3]) # receive 'ok' buffer = None response = str() while 1: buffer = s.recv(1) if buffer == '': break else: response = response + buffer if response == 'ok': print 'receiver acknowledged receipt of filename' # send file s.send(f.read()) elif response == 'no': print "receiver doesn't want the file" # cleanup f.close() s.close() Receiver: from jmm_sockets import * s = getServerSocket(None, 16001) conn, addr = s.accept() buffer = None filename = str() # receive filename while 1: buffer = conn.recv(1) if buffer == '': break else: filename = filename + buffer print "sender wants to send", filename, "is that ok?" user_choice = raw_input("ok/no: ") if user_choice == 'ok': # send ok conn.send('ok') #receive file data = str() while 1: buffer = conn.recv(1) if buffer=='': break else: data = data + buffer print data else: conn.send('no') conn.close() I'm sure I'm missing something here in the sorts of a deadlock, but don't know what it is.

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• python send/receive hex data via TCP socket

  - by Mike

  I have a ethenet access control device that is said to be able to communicate via TCP. How can i send a pachet by entering the HEX data, since this is what i have from their manual (a standard format for the communication packets sent and received after each command)

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• Send serialised object via socket

  - by RubbleFord

  Whats the best way to format a message to a server, at moment I'm serilising an object using the binaryformatter and then sending it to the server. At the server end its listening in an async fashion and then when the buffer size recieved is not 100% it assumes that the transfer has complete. This is working and the moment, and I can deserialise the object at the other end, I'm just concerned that if I start sending async this method will fail has message's could be blurred. I know that I need to mark the message somehow as to say that's the end of message one, this other bit belongs to message 2, but I'm unsure of the correct way to do this. Could anyone point me in the right direction and maybe give me some examples? Thanks

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• Migrating Ajax web application to web socket

  - by Bastan

  Hi, I think i'm just missing a little detail that is preventing me from seeing the whole picture. I have a web application which use ajax request every x time to update client with new information or tasks. I also have a long running process on the server which is a java computation engine. I would like this engine to send update to the client. I am wondering how to migrate my web app to using websocket. Probably phpwebsocket or similar. Can my server 'decide' to send information to a specific client? It seems possible looking at the php-websocket. Can my java backend long process use the websocket server to send notification to a specific client. How? well I can say that my java app could use a class that could send over websocket instead of http. But how the websocket server knows to which client to send the 'info'. I am puzzle by all this. Any document that explain this in more details? It seems that the websocket could create an instance of my web application. Thanks

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• Java socket bug on linux (0xFF sent, -3 received)

  - by Marius

  While working on a WebSocket server in Java I came across this strange bug. I've reduced it down to two small java files, one is the server, the other is the client. The client simply sends 0x00, the string Hello and then 0xFF (per the WebSocket specification). On my windows machine, the server prints the following: Listening byte: 0 72 101 108 108 111 recieved: 'Hello' While on my unix box the same code prints the following: Listening byte: 0 72 101 108 108 111 -3 Instead of receiving 0xFF it gets -3, never breaks out of the loop and never prints what it has received. The important part of the code looks like this: byte b = (byte)in.read(); System.out.println("byte: "+b); StringBuilder input = new StringBuilder(); b = (byte)in.read(); while((b & 0xFF) != 0xFF){ input.append((char)b); System.out.print(b+" "); b = (byte)in.read(); } inputLine = input.toString(); System.out.println("recieved: '" + inputLine+"'"); if(inputLine.equals("bye")){ break; } I've also uploaded the two files to my server: Server.java Client.java My Windows machine is running windows 7 and my Linux machine is running Debian

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• Increase a recive buffer in UDP socket

  - by unresolved_external

  I'wm writing an app, which transmits video and obviously uses UDP protocol fot this purpose. So I am wondering how can I increase a size of send/recieve buffer, cause currently the maximal size of data, which I can send is 65000 bytes. I already tried to do it in following way: int option = 262144; if(setsockopt(m_SocketHandle,SOL_SOCKET,SO_RCVBUF ,(char*)&option,sizeof(option)) < 0) { printf("setsockopt failed\n"); } But it did not work. So how can I do it?

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• C# Client-Server implementation error on client's socket

  - by Ksice

  I'm trying to launch my client. Server already runned on the same computer. So I'm using "localhost" with GetHostEntry: IPHostEntry ipHostInfo = System.Net.Dns.GetHostEntry("localhost"); IPAddress ipAddress = ipHostInfo.AddressList[0]; IPEndPoint remoteEP = new IPEndPoint(ipAddress, Port); But I have this "no connection could be made because the target machine actively refused it" error. What is the reason? Could it be because ipHostInfo.AddressList[0] is an IPv6? How then I can accept Ipv4 address?

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• Portable Socket programming in C/C++ possible?

  - by questions

  I am thinking of creating a multi-platform portable C++ server-client application. Is it even possible while using only standard libraries? If no, what other libraries are there? Are there any improvements in this direction in C++11x? Like for threads, now we have std::threads. To make it more clear.. I want something like boost::thread, which provides multiplatform portable multithreading, for networking. And why C++ doesn't have libraries(standard) for such basic things like networking?

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• Sending compres data via socket

  - by Pizza

  Hi, I have to make a log server in java, and one task is to send the data compressed. Now I am sending it line by line in plain text, but I must compress it. The server handle "HTTP like" request. For example, I can get a log sending "GET xxx.log". This will entablish a TCP connection to the server, the server response with a header and the log, and close the connection. The client, reads line by line and analyzes each LOG entry. I tried some ways without success. My main problem is that I don't know where each line ends(in the client size). Any idea?

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• Sending information down a socket in C#

  - by markyoung1984

  I have built two programs in C# and I am sending simple strings through the sockets. This is fine for the moment but in the near future I will need to send more complicated items, such as objects down the sockets and eventually files. What steps would I take to do this? What purpose do the buffers serve for the sockets/streams? Apologies if I am a little vague.

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• How to open multiple socket connections and do callbacks in PHP

  - by Click Upvote

  I'm writing some code which processes a queue of items. The way it works is this: Get the next item flagged as needing to be processed from the mysql database row. Request some info from a google API using Curl, wait until the info is returned. Do the remainder of the processing based on the info returned. Flag the item as processed in the db, move onto the next item. The problem is that on step # 2. Google sometimes takes 10-15 seconds to return the requested info, during this time my script has to remain halted and wait. I'm wondering if I could change the code to do the following instead: Get the next 5 items to be processed as usual. Request info for items 1-5 from google, one after the other. When the info for item 1 is returned, a 'callback' should be done which calls up a function or otherwise calls some code which then does the remainder of the processing on items 1-5. And then the script starts over until all pending items in db are marked processed. How can something like this be achieved?

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• Delphi How to wait for socket answer inside procedure?

  - by Astronavigator

  For some specific needs i need to create procedure that waits for socket request (or answer) in dll: TForm1 = class(TForm) ServerSocket1: TServerSocket; ...... procedure MyWaitProc; stdcall; begin Go := false; while not Go do begin // Wating... // Application.ProcessMessages; // Works with this line end; end; procedure TForm1.ServerSocket1ClientRead(Sender: TObject; Socket: TCustomWinSocket); begin MessageBoxA(0, PAnsiChar('Received: '+Socket.ReceiveText), '', MB_OK); Go := true; end; exports MyWaitProc; When I call Application.ProcessMessages everything works fine: application waits for request and then continues. But in my case calling Application.ProcessMessages causes to unlocking main form on host application (not dll's one). When I don't call Application.ProcessMessages application just hangs couse it cannot handle message... So, how to create such a procedure that's wating for socket answer ? Maybe there a way to wait for socket answer without using Application.ProcessMessages ? EDIT I also tried to use TIdTCPServer, for some reasons, the result is the same. TForm1 = class(TForm) IdTCPServer1: TIdTCPServer; ..... procedure MyWaitProc; stdcall; begin Go := false; while not Go do begin // Waiting ... // Application.ProcessMessages; end; end; procedure TForm1.IdTCPServer1Execute(AContext: TIdContext); var s: string; begin s := AContext.Connection.Socket.ReadString(1); AllText := AllText + s; Go := True; end;

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