Beej's Guide to Network Programming Using Internet Sockets

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Beej’s Guide to Network Programming Using Internet Sockets 67Return ValueReturns the number of bytes actually sent, or -1 on error (and errno will be set accordingly.)Note that the number of bytes actually sent might be less than the number you asked it to send!See the section on handling partial send()s for a helper function to get around this.Also, if the socket has been closed by either side, the process calling send() will get the signalSIGPIPE. (Unless send() was called with the MSG_NOSIGNAL flag.)Exampleint spatula_count = 3490;char *secret_message = "The Cheese is in The Toaster";int stream_socket, dgram_socket;struct sockaddr_in dest;int temp;// first with TCP stream sockets:stream_socket = socket(PF_INET, SOCK_STREAM, 0);.// convert to network byte ordertemp = htonl(spatula_count);// send data normally:send(stream_socket, &temp, sizeof(temp), 0);// send secret message out of band:send(stream_socket, secret_message, strlen(secret_message)+1, MSG_OOB);// now with UDP datagram sockets:dgram_socket = socket(PF_INET, SOCK_DGRAM, 0);.// build destinationdest.sin_family = AF_INET;inet_aton("10.0.0.1", &dest.sin_addr);dest.sin_port = htons(2223);// send secret message normally:sendto(dgram_socket, secret_message, strlen(secret_message)+1, 0,(struct sockaddr*)&dest, sizeof(dest));See Alsorecv(), recvfrom()
Beej’s Guide to Network Programming Using Internet Sockets 688.19. shutdown()Stop further sends and recieves on a socketPrototypes#include int shutdown(int s, int how);DescriptionThat’s it! I’ve had it! No more send()s are allowed on this socket, but I still want to recv()data on it! Or vice-versa! How can I do this?When you close() a socket descriptor, it closes both sides of the socket for reading andwriting, and frees the socket descriptor. If you just want to close one side or the other, you can usethis shutdown() call.As for parameters, s is obviously the socket you want to perform this action on, and what actionthat is can be specified with the how paramter. How can be SHUT_RD to prevent further recv()s,SHUT_WR to prohibit further send()s, or SHUT_RDWR to do both.Note that shutdown() doesn’t free up the socket descriptor, so you still have to eventuallyclose() the socket even if it has been fully shut down.This is a rarely used system call.Return ValueReturns zero on success, or -1 on error (and errno will be set accordingly.)Exampleint s = socket(PF_INET, SOCK_STREAM, 0);// ...do some send()s and stuff in here...// and now that we’re done, don’t allow any more sends()s:shutdown(s, SHUT_RD);See Alsoclose()
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