server.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <unistd.h>
   4 #include <errno.h>
   5 #include <string.h>
   6 #include <sys/types.h>
   7 #include <sys/socket.h>
   8 #include <netinet/in.h>
   9 #include <netdb.h>
  10 #include <arpa/inet.h>
  11 #include <sys/wait.h>
  12 #include <signal.h>
  13
  14 #define PORT "3490"  // the port users will be connecting to
  15
  16 #define BACKLOG 10       // how many pending connections queue will hold
  17
  18 void sigchld_handler(int s)
  19 {
  20         while(waitpid(-1, NULL, WNOHANG) > 0);
  21 }
  22
  23 // get sockaddr, IPv4
  24 void *get_in_addr(struct sockaddr *sa)
  25 {
  26         if (sa->sa_family == AF_INET) {
  27                 return &(((struct sockaddr_in*)sa)->sin_addr);
  28         }
  29 }
  30
  31 int main(void)
  32 {
  33         int sockfd, activefd;  // listen on sockfd, new connection on activefd
  34         struct addrinfo hints, *servinfo, *p;
  35         struct sockaddr_storage their_addr; // connector's address information
  36         socklen_t sin_size;
  37         struct sigaction sa;
  38         int yes=1;
  39         char source[INET6_ADDRSTRLEN];
  40 //    char CLIENT_IP[15] = "107.21.205.69\0";
  41         int rv;
  42
  43         memset(&hints, 0, sizeof hints); // make sure the struct is empty
  44         hints.ai_family = AF_INET; // IPv4
  45         hints.ai_socktype = SOCK_STREAM;
  46         hints.ai_flags = AI_PASSIVE; // use my IP
  47
  48         if ((rv = getaddrinfo(NULL, PORT, &hints, &servinfo)) != 0) {
  49                 fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
  50                 return 1;
  51         }
  52
  53     // servinfo now points to a linked list of 1 or more struct addrinfos
  54
  55         // loop through all the results and bind to the first we can
  56         for(p = servinfo; p != NULL; p = p->ai_next) {
  57                 if ((sockfd = socket(p->ai_family, p->ai_socktype,
  58                                 p->ai_protocol)) == -1) {
  59                         perror("server: socket");
  60                         continue;
  61                 }
  62
  63                 if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes,
  64                                 sizeof(int)) == -1) {
  65                         perror("setsockopt");
  66                         exit(1);
  67                 }
  68
  69                 if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
  70                         close(sockfd);
  71                         perror("server: bind");
  72                         continue;
  73                 }
  74
  75                 break;
  76         }
  77
  78         if (p == NULL)  {
  79                 fprintf(stderr, "server: failed to bind\n");
  80                 return 2;
  81         }
  82
  83         freeaddrinfo(servinfo); // all done with this structure
  84
  85         if (listen(sockfd, BACKLOG) == -1) {
  86                 perror("listen");
  87                 exit(1);
  88         }
  89
  90         sa.sa_handler = sigchld_handler; // reap all dead processes
  91         sigemptyset(&sa.sa_mask);
  92         sa.sa_flags = SA_RESTART;
  93         if (sigaction(SIGCHLD, &sa, NULL) == -1) {
  94                 perror("sigaction");
  95                 exit(1);
  96         }
  97
  98         printf("server: waiting for connections...\n");
  99
 100         while(1) {  // main accept() loop
 101                 sin_size = sizeof their_addr;
 102                 activefd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size);
 103                 if (activefd == -1) {
 104                         perror("accept");
 105                         continue;
 106                 }
 107
 108                 inet_ntop(their_addr.ss_family,
 109                         get_in_addr((struct sockaddr *)&their_addr),
 110                         source, sizeof source);
 111
 112         if (strcmp(source, "107.21.205.69") != 0 &&
 113                 strcmp(source, "127.0.0.1") != 0){
 114             close(activefd);
 115             continue;
 116         }
 117
 118                 if (!fork()) { // this is the child process
 119                         close(sockfd); // child doesn't need the listener
 120             char buf[4096];
 121             if (recv(activefd, buf, 99, 0) == -1) {
 122                 perror("recv");
 123                 exit(1);
 124             }
 125             buf[4096] = '\0';
 126             printf("server: recieved '%s'\n", buf);
 127             if (!fork()){
 128                 setenv("DISPLAY", ":0", 1); // doesn't seem to be doing the trick
 129                 execl("notify-display",
 130                         "notify-display", buf, NULL);
 131             // the first argument to execl is the command, the second is the first argument
 132             // passed to the program ($0), customarily the evocation of the command
 133             }
 134                         close(activefd);
 135                         exit(0);
 136                 }
 137                 close(activefd);
 138         }
 139
 140         return 0;
 141 }