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/* PLEASE READ THE FILE NB-APOLOGY!!!! There are some things you should know about this source before you read it. Thanks. Quang Ngo alerted me to a bug where the variable listnum in deal_with_data() wasn't being passed in by parameter, thus it was always garbage. I have quick-fixed this in the code below. - Spencer (October 12, 1999) Non blocking server demo By Vic Metcalfe (vic@acm.org) For the unix-socket-faq */ #include "sockhelp.h" #include <ctype.h> #include <sys/time.h> #include <fcntl.h> int sock; /* The socket file descriptor for our "listening" socket */ int connectlist[5]; /* Array of connected sockets so we know who we are talking to */ fd_set socks; /* Socket file descriptors we want to wake up for, using select() */ int highsock; /* Highest #'d file descriptor, needed for select() */ void setnonblocking(sock) int sock; { int opts; opts = fcntl(sock,F_GETFL); if (opts < 0) { perror("fcntl(F_GETFL)"); exit(EXIT_FAILURE); } opts = (opts | O_NONBLOCK); if (fcntl(sock,F_SETFL,opts) < 0) { perror("fcntl(F_SETFL)"); exit(EXIT_FAILURE); } return; } void build_select_list() { int listnum; /* Current item in connectlist for for loops */ /* First put together fd_set for select(), which will consist of the sock veriable in case a new connection is coming in, plus all the sockets we have already accepted. */ /* FD_ZERO() clears out the fd_set called socks, so that it doesn't contain any file descriptors. */ FD_ZERO(&socks); /* FD_SET() adds the file descriptor "sock" to the fd_set, so that select() will return if a connection comes in on that socket (which means you have to do accept(), etc. */ FD_SET(sock,&socks); /* Loops through all the possible connections and adds those sockets to the fd_set */ for (listnum = 0; listnum < 5; listnum++) { if (connectlist[listnum] != 0) { FD_SET(connectlist[listnum],&socks); if (connectlist[listnum] > highsock) highsock = connectlist[listnum]; } } } void handle_new_connection() { int listnum; /* Current item in connectlist for for loops */ int connection; /* Socket file descriptor for incoming connections */ /* We have a new connection coming in! We'll try to find a spot for it in connectlist. */ connection = accept(sock, NULL, NULL); if (connection < 0) { perror("accept"); exit(EXIT_FAILURE); } setnonblocking(connection); for (listnum = 0; (listnum < 5) && (connection != -1); listnum ++) if (connectlist[listnum] == 0) { printf("\nConnection accepted: FD=%d; Slot=%d\n", connection,listnum); connectlist[listnum] = connection; connection = -1; } if (connection != -1) { /* No room left in the queue! */ printf("\nNo room left for new client.\n"); sock_puts(connection,"Sorry, this server is too busy. " Try again later!\r\n"); close(connection); } } void deal_with_data( int listnum /* Current item in connectlist for for loops */ ) { char buffer[80]; /* Buffer for socket reads */ char *cur_char; /* Used in processing buffer */ if (sock_gets(connectlist[listnum],buffer,80) < 0) { /* Connection closed, close this end and free up entry in connectlist */ printf("\nConnection lost: FD=%d; Slot=%d\n", connectlist[listnum],listnum); close(connectlist[listnum]); connectlist[listnum] = 0; } else { /* We got some data, so upper case it and send it back. */ printf("\nReceived: %s; ",buffer); cur_char = buffer; while (cur_char[0] != 0) { cur_char[0] = toupper(cur_char[0]); cur_char++; } sock_puts(connectlist[listnum],buffer); sock_puts(connectlist[listnum],"\n"); printf("responded: %s\n",buffer); } } void read_socks() { int listnum; /* Current item in connectlist for for loops */ /* OK, now socks will be set with whatever socket(s) are ready for reading. Lets first check our "listening" socket, and then check the sockets in connectlist. */ /* If a client is trying to connect() to our listening socket, select() will consider that as the socket being 'readable'. Thus, if the listening socket is part of the fd_set, we need to accept a new connection. */ if (FD_ISSET(sock,&socks)) handle_new_connection(); /* Now check connectlist for available data */ /* Run through our sockets and check to see if anything happened with them, if so 'service' them. */ for (listnum = 0; listnum < 5; listnum++) { if (FD_ISSET(connectlist[listnum],&socks)) deal_with_data(listnum); } /* for (all entries in queue) */ } int main (argc, argv) int argc; char *argv[]; { char *ascport; /* ASCII version of the server port */ int port; /* The port number after conversion from ascport */ struct sockaddr_in server_address; /* bind info structure */ int reuse_addr = 1; /* Used so we can re-bind to our port while a previous connection is still in TIME_WAIT state. */ struct timeval timeout; /* Timeout for select */ int readsocks; /* Number of sockets ready for reading */ /* Make sure we got a port number as a parameter */ if (argc < 2) { printf("Usage: %s PORT\r\n",argv[0]); exit(EXIT_FAILURE); } /* Obtain a file descriptor for our "listening" socket */ sock = socket(AF_INET, SOCK_STREAM, 0); if (sock < 0) { perror("socket"); exit(EXIT_FAILURE); } /* So that we can re-bind to it without TIME_WAIT problems */ setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &reuse_addr, sizeof(reuse_addr)); /* Set socket to non-blocking with our setnonblocking routine */ setnonblocking(sock); /* Get the address information, and bind it to the socket */ ascport = argv[1]; /* Read what the user gave us */ port = atoport(ascport); /* Use function from sockhelp to convert to an int */ memset((char *) &server_address, 0, sizeof(server_address)); server_address.sin_family = AF_INET; server_address.sin_addr.s_addr = htonl(INADDR_ANY); server_address.sin_port = port; if (bind(sock, (struct sockaddr *) &server_address, sizeof(server_address)) < 0 ) { perror("bind"); close(sock); exit(EXIT_FAILURE); } /* Set up queue for incoming connections. */ listen(sock,5); /* Since we start with only one socket, the listening socket, it is the highest socket so far. */ highsock = sock; memset((char *) &connectlist, 0, sizeof(connectlist)); while (1) { /* Main server loop - forever */ build_select_list(); timeout.tv_sec = 1; timeout.tv_usec = 0; /* The first argument to select is the highest file descriptor value plus 1. In most cases, you can just pass FD_SETSIZE and you'll be fine. */ /* The second argument to select() is the address of the fd_set that contains sockets we're waiting to be readable (including the listening socket). */ /* The third parameter is an fd_set that you want to know if you can write on -- this example doesn't use it, so it passes 0, or NULL. The fourth parameter is sockets you're waiting for out-of-band data for, which usually, you're not. */ /* The last parameter to select() is a time-out of how long select() should block. If you want to wait forever until something happens on a socket, you'll probably want to pass NULL. */ readsocks = select(highsock+1, &socks, (fd_set *) 0, (fd_set *) 0, &timeout); /* select() returns the number of sockets that had things going on with them -- i.e. they're readable. */ /* Once select() returns, the original fd_set has been modified so it now reflects the state of why select() woke up. i.e. If file descriptor 4 was originally in the fd_set, and then it became readable, the fd_set contains file descriptor 4 in it. */ if (readsocks < 0) { perror("select"); exit(EXIT_FAILURE); } if (readsocks == 0) { /* Nothing ready to read, just show that we're alive */ printf("."); fflush(stdout); } else read_socks(); } /* while(1) */ } /* main */
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