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POBittorrent Client in C++, Connecting to Peer on Non-Blocking socket always times out
 

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  1. POBittorrent Client in C++, Connecting to Peer on Non-Blocking socket always times out
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    <p>EDIT::</p> <p>So the answer I accepted below was not actually the issue. I verified through wireshark that the peers are indeed transmitting over TCP for torrent downloads. So I should be able to connect, but all attempts timeout...</p> <hr> <p>So I'm making a bittorrent client in C++ and I'm using the BSD sockets library for all network communications. I have some code to connect to peers over TCP but every attempt times out. I am 100% certain the peers are valid for the file I'm seeking to download, I started downloading the file in Transmission and the same peers were being connected to.</p> <p>Here is my connect code, the first part is simply adding a bunch of peers to a vector so I can iterate over it and try each peer: </p> <p>(NOTE" all of the upper-case system calls are just wrapper functions for error handling purposes. There isn't any funny business happening there.)</p> <pre><code> char * HOST; uint16_t PORT; std::vector&lt;char *&gt; all_ips; std::vector&lt;uint16_t&gt; all_ports; all_ips.push_back("213.112.225.102"); all_ports.push_back(18715); uint32_t i = 0; for (; i &lt; all_ips.size(); i++) { HOST = all_ips[i]; PORT = all_ports[i]; struct sockaddr * saddr; struct sockaddr_in addr; struct addrinfo hints, * ai, * it; char strportnum[25]; memset(&amp;hints, '\0', sizeof(hints)); hints.ai_flags = AI_ADDRCONFIG; hints.ai_socktype = SOCK_STREAM; snprintf(strportnum, 10, "%d", PORT); GetAddrInfo(HOST, strportnum, &amp;hints, &amp;ai); for (it = ai; it != NULL; it = it-&gt;ai_next) { if ((sockFd = Socket(AF_INET, SOCK_STREAM, 0)) != -1) { saddr = ai-&gt;ai_addr; saddr-&gt;sa_family = AF_INET; int res; long arg; fd_set myset; struct timeval tv; int valopt; socklen_t lon; // Set non-blocking if( (arg = fcntl(sockFd, F_GETFL, NULL)) &lt; 0) { fprintf(stderr, "Error fcntl(..., F_GETFL) (%s)\n", strerror(errno)); exit(0); } arg |= O_NONBLOCK; if( fcntl(sockFd, F_SETFL, arg) &lt; 0) { fprintf(stderr, "Error fcntl(..., F_SETFL) (%s)\n", strerror(errno)); exit(0); } // Trying to connect with timeout res = Connect(sockFd, saddr, sizeof(*saddr)); if (res &lt; 0) { if (errno == EINPROGRESS) { fprintf(stderr, "EINPROGRESS in connect() - selecting\n"); do { //Set timeouts tv.tv_sec = 20; tv.tv_usec = 0; FD_ZERO(&amp;myset); FD_SET(sockFd, &amp;myset); res = Select(sockFd + 1, NULL, &amp;myset, NULL, &amp;tv); if (res &lt; 0 &amp;&amp; errno != EINTR) { fprintf(stderr, "Error connecting %d - %s\n", errno, strerror(errno)); break; } else if (res &gt; 0) { // Socket selected for write lon = sizeof(int); if (getsockopt(sockFd, SOL_SOCKET, SO_ERROR, (void*)(&amp;valopt), &amp;lon) &lt; 0) { fprintf(stderr, "Error in getsockopt() %d - %s\n", errno, strerror(errno)); break; } // Check the value returned... if (valopt) { fprintf(stderr, "Error in delayed connection() %d - %s\n", valopt, strerror(valopt)); break; } break; } else { fprintf(stderr, "Timeout in select() - Cancelling!\n"); break; } } while (1); } else { fprintf(stderr, "Error connecting %d - %s\n", errno, strerror(errno)); break; } } // Set to blocking mode again... if( (arg = fcntl(sockFd, F_GETFL, NULL)) &lt; 0) { fprintf(stderr, "Error fcntl(..., F_GETFL) (%s)\n", strerror(errno)); break; } arg &amp;= (~O_NONBLOCK); if(fcntl(sockFd, F_SETFL, arg) &lt; 0) { fprintf(stderr, "Error fcntl(..., F_SETFL) (%s)\n", strerror(errno)); break; } } } freeaddrinfo(ai); } </code></pre> <p>I've been using this site as a guide to non-blocking sockets: <a href="http://developerweb.net/viewtopic.php?id=3196" rel="nofollow">http://developerweb.net/viewtopic.php?id=3196</a></p>
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    1. COWhat happens when you try to connect to a localhost service? E.g. starting a listener with netcat, and use your code to connect?
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      1. POBittorrent Client in C++, Connecting to Peer on Non-Blocking socket always times out
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    2. COCould it be your trying to connect using TCP to a port expecting to "be spoken" UDP with?
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    3. COFor reference: http://en.wikipedia.org/wiki/Micro_Transport_Protocol
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