server.c

   1 /*
   2 ** server.c -- a stream socket server demo
   3 */
   4
   5 #include <stdio.h>
   6 #include <stdlib.h>
   7 #include <unistd.h>
   8 #include <errno.h>
   9 #include <string.h>
  10 #include <sys/types.h>
  11 #include <sys/socket.h>
  12 #include <netinet/in.h>
  13 #include <netdb.h>
  14 #include <arpa/inet.h>
  15 #include <sys/wait.h>
  16 #include <signal.h>
  17
  18 #define PORT "3490"  // the port users will be connecting to
  19
  20 #define BACKLOG 10       // how many pending connections queue will hold
  21
  22 void sigchld_handler(int s)
  23 {
  24         while(waitpid(-1, NULL, WNOHANG) > 0);
  25 }
  26
  27 // get sockaddr, IPv4 or IPv6:
  28 void *get_in_addr(struct sockaddr *sa)
  29 {
  30         if (sa->sa_family == AF_INET) {
  31                 return &(((struct sockaddr_in*)sa)->sin_addr);
  32         }
  33
  34         return &(((struct sockaddr_in6*)sa)->sin6_addr);
  35 }
  36
  37 int main(void)
  38 {
  39         int sockfd, new_fd;  // listen on sock_fd, new connection on new_fd
  40         struct addrinfo hints, *servinfo, *p;
  41         struct sockaddr_storage their_addr; // connector's address information
  42         socklen_t sin_size;
  43         struct sigaction sa;
  44         int yes=1;
  45         char s[INET6_ADDRSTRLEN];
  46         int rv;
  47
  48         memset(&hints, 0, sizeof hints);
  49         hints.ai_family = AF_UNSPEC;
  50         hints.ai_socktype = SOCK_STREAM;
  51         hints.ai_flags = AI_PASSIVE; // use my IP
  52
  53         if ((rv = getaddrinfo(NULL, PORT, &hints, &servinfo)) != 0) {
  54                 fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
  55                 return 1;
  56         }
  57
  58         // loop through all the results and bind to the first we can
  59         for(p = servinfo; p != NULL; p = p->ai_next) {
  60                 if ((sockfd = socket(p->ai_family, p->ai_socktype,
  61                                 p->ai_protocol)) == -1) {
  62                         perror("server: socket");
  63                         continue;
  64                 }
  65
  66                 if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes,
  67                                 sizeof(int)) == -1) {
  68                         perror("setsockopt");
  69                         exit(1);
  70                 }
  71
  72                 if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
  73                         close(sockfd);
  74                         perror("server: bind");
  75                         continue;
  76                 }
  77
  78                 break;
  79         }
  80
  81         if (p == NULL)  {
  82                 fprintf(stderr, "server: failed to bind\n");
  83                 return 2;
  84         }
  85
  86         freeaddrinfo(servinfo); // all done with this structure
  87
  88         if (listen(sockfd, BACKLOG) == -1) {
  89                 perror("listen");
  90                 exit(1);
  91         }
  92
  93         sa.sa_handler = sigchld_handler; // reap all dead processes
  94         sigemptyset(&sa.sa_mask);
  95         sa.sa_flags = SA_RESTART;
  96         if (sigaction(SIGCHLD, &sa, NULL) == -1) {
  97                 perror("sigaction");
  98                 exit(1);
  99         }
 100
 101         printf("server: waiting for connections...\n");
 102
 103         while(1) {  // main accept() loop
 104                 sin_size = sizeof their_addr;
 105                 new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size);
 106                 if (new_fd == -1) {
 107                         perror("accept");
 108                         continue;
 109                 }
 110
 111                 inet_ntop(their_addr.ss_family,
 112                         get_in_addr((struct sockaddr *)&their_addr),
 113                         s, sizeof s);
 114                 printf("server: got connection from %s\n", s);
 115
 116                 if (!fork()) { // this is the child process
 117                         close(sockfd); // child doesn't need the listener
 118             char buf[100];
 119             if (recv(new_fd, buf, 99, 0) == -1) {
 120                 perror("recv");
 121                 exit(1);
 122             }
 123             buf[100] = '\0';
 124             printf("server: recieved '%s'\n", buf);
 125             if (!fork())
 126                 execl("/home/dylan/test", "irssi", buf, NULL);
 127                         close(new_fd);
 128                         exit(0);
 129                 }
 130                 close(new_fd);  // parent doesn't need this
 131         }
 132
 133         return 0;
 134 }
 135