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POWriting to closed TCP/IP connection hangs
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copied!<p>My TCP/IP client hangs while writing to socket. This happens even if server properly closes an accepted connection with <code>close()</code> (or with <code>shutdown()</code>) call. I've always thought that write should return with ECONNRESET error for this case. </p> <p>How do i prevent hang ups in synchronous output? Or rather what am I doing wrong so that an error is not reported by <code>write()</code>?</p> <p>Should I use <code>send()</code> instead of <code>write()</code> or they are interchangeable?</p> <p>I'm testing networking in a separate application with two threads. Main thread starts server thread, that accepts connection and immediately closes it. Main thread then imitates client behavior by connecting to listening port.</p> <p>Main thread code:</p> <pre><code>sockaddr_in serv_addr; bzero((char *) &serv_addr, sizeof(serv_addr)); serv_addr.sin_family = AF_INET; serv_addr.sin_addr.s_addr = INADDR_ANY; serv_addr.sin_port = htons(port); int s = socket(AF_INET, SOCK_STREAM, 0); if (bind(s, (sockaddr*)(&serv_addr), sizeof(serv_addr)) < 0) { close(s); throw runtime_error(strerror(errno)); } listen(s,1); start_thread(s); // posix thread accepting a connection on s is started here //Code below imitates TCP/IP client struct hostent *hp; struct sockaddr_in addr; if((hp = gethostbyname(host.c_str())) == NULL){ throw HErrno(); } bcopy(hp->h_addr, &addr.sin_addr, hp->h_length); addr.sin_port = htons(port); addr.sin_family = AF_INET; int _socket = ::socket(PF_INET, SOCK_STREAM, IPPROTO_TCP); if (_socket < 0) { throw Errno(); } assert(ENOTCONN==107); assert(_socket>=0); if(::connect(_socket, (const struct sockaddr *)&addr, sizeof(struct sockaddr_in)) == -1){ throw Errno(); } while(true) { const char a[] = "pattern"; if (write( _socket, a, 7)<0) // Writes 30000 times, then hangs break; } </code></pre> <p>Server thread code:</p> <pre><code>int connection = accept(s); close(connection); </code></pre> <p><strong>EDIT:</strong> The problem reduced to my programming error. It seems I've failed to start accepting thread properly.</p>

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