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POselect() invalid argument
 

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  1. POselect() invalid argument
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    <p>I have an array of 6 sockets, each designed to listen for incoming messages. On each socket, I need to call select() to listen for incoming messages. This code compiles, but when I run it, I get a message </p> <p><code>select failure: Invalid argument</code></p> <p><code>errno: 22</code></p> <p>Can anyone see what I am doing wrong? Thanks!</p> <p>This code is in int main():</p> <pre><code>int listenfd[6]; fd_set read_set; struct timeval tv; time_t start_time; make_connections(listenfd, neighbor, servAddr, read_set); FD_ZERO(&amp;read_set); // add the accepted connections to the read set for use with select() for (i=0; i&lt;6; i++) { FD_SET(listenfd[i], &amp;read_set); } tv.tv_sec = 5; // seconds tv.tv_usec = 5000000; // microseconds gettimeofday(&amp;tv, NULL); start_time = tv.tv_sec; // EDIT: made the following change per suggestion by ThePelaton // same error exists, though //if ( (select(6, &amp;read_set, NULL, NULL, &amp;tv)) == -1) { int max = listenfd[0]; for (i=1; i&lt;6; i++) { if (listenfd[i] &gt; listenfd[i-1]) { max = i; } } if ( (select(listenfd[max]+1, &amp;read_set, NULL, NULL, &amp;tv)) == -1) { perror("select failure"); fprintf(stdout, "errno: %d\n", errno); exit(EXIT_FAILURE); } </code></pre> <p>My other function:</p> <pre><code>void make_connections(int listenfd[6], Neighbor neighbor[6], struct sockaddr_in servAddr, fd_set read_set) { int num_hosts = 6; int i, rc, on=1; struct sockaddr_storage their_addr; socklen_t addr_size; for (i=0; i&lt;6; i++) { // Create one socket for each neighbor if((listenfd[i] = socket(AF_INET, SOCK_STREAM, 0)) &lt; 0) { exit(1); } /*************************************************************/ /* Allow socket descriptor to be reuseable */ /*************************************************************/ rc = setsockopt(listenfd[i], SOL_SOCKET, SO_REUSEADDR, (char *)&amp;on, sizeof(on)); if (rc &lt; 0) { perror("setsockopt() failed"); close(listenfd[i]); exit(-1); } /*************************************************************/ /* Set socket to be non-blocking. All of the sockets for */ /* the incoming connections will also be non-blocking since */ /* they will inherit that state from the listening socket. */ /*************************************************************/ rc = ioctl(listenfd[i], FIONBIO, (char *)&amp;on); if (rc &lt; 0) { perror("ioctl() failed"); close(listenfd[i]); exit(-1); } /* get server IP address (input must be IP address, not DNS name) */ bzero(&amp;servAddr,sizeof(servAddr)); //zero the struct servAddr.sin_family = AF_INET; //address family (ipv4) servAddr.sin_port = htons(neighbor.port); //sets port to network byte order servAddr.sin_addr.s_addr = INADDR_ANY; // first attempt to bind / listen on each port if (bind(listenfd[i], (struct sockaddr *)&amp;servAddr, sizeof(servAddr)) &lt; 0) { perror("bind failed"); exit (-1); } if (listen(listenfd[i], 10) &lt; 0) { perror("listen() failed"); exit (-1); } } } </code></pre> <p>EDIT 2: Pretty sure that I figured this out. I was using my time value (tv) to do some timestamping of my process. Looks like that is where the invalid argument comes from, not from the sockets.</p>
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    1. COPerhaps the `struct timeval` doesn't like having 5000000 (5 seconds) as part of the tv_usec field? What timeout value do you want?
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    2. COAt the moment, I don't really care about what value this is. I've tried a few different values here, but I get the same result every time.
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    3. COActually, I just checked with a large tv_usec example on a Linux kernel and it appears to work as expected. In your example, the max delay would be 10 seconds. I don't think this is your issue, see ThePelaton's answer.
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