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POC socket programming: calling recv() changes my socket file descriptor?
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copied!<p>Hey all, I have this strange problem with recv(). I'm programming client/server where client send() a message (a structure to be exact) and server recv() it. I am also working with multiple sockets and select(). </p> <pre><code>while(1) { readset = info->read_set; info->copy_set = info->read_set; timeout.tv_sec = 1; timeout.tv_usec = 0; // 0.5 seconds ready = select(info->max_fd+1, &readset, NULL, NULL, &timeout); if (ready == -1) { printf("S: ERROR: select(): %s\nEXITING...", strerror(errno)); exit(1); } else if (ready == 0) { continue; } else { printf("S: oh finally you have contacted me!\n"); for(i = 0; i < (info->max_fd+1); i++) { if(FD_ISSET(i, &readset)) //this is where problem begins { printf("S: %i is set\n", i); printf("S: we talking about socket %i son\n", i); // i = 4 num_bytes = recv(i, &msg, MAX_MSG_BYTE, 0); printf("S: number of bytes recieved in socket %i is %i\n", i, num_bytes); // prints out i = 0 what?? if (num_bytes == 0) { printf("S: socket has been closed\n"); break; } else if (num_bytes == -1) { printf("S: ERROR recv: %d %s \n", i, strerror(errno)); continue; } else { handle_request(arg, &msg); printf("S: msg says %s\n", msg->_payload); } } // if (FD_ISSET(i, &readset) else printf("S: %i is not set\n", i); } // for (i = 0; i < maxfd+1; i++) to check sockets for msg } // if (ready == -1) info->read_set = info->copy_set; printf("S: copied\n"); } </code></pre> <p>the problem I have is that in <code>read_set</code>, 0~3 aren't set and 4 is. That is fine. But when i call <code>recv()</code>, <code>i</code> suddently becomes 0. Why is that? It doesn't make sense to me why <code>recv()</code> would take an socket file descriptor number and modify to another number. Is that normal? Am I missing something?</p> <pre><code>S: 0 is not set S: 1 is not set S: 2 is not set S: 3 is not set S: 4 is set S: we talking about socket 4 son S: i is strangely or unstrangely 0 S: number of bytes recieved in socket 0 is 40 </code></pre> <p>That's what it prints out.</p>

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