client.c

   1 /*
   2 ** client.c -- a stream socket client 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 <netdb.h>
  11 #include <sys/types.h>
  12 #include <netinet/in.h>
  13 #include <sys/socket.h>
  14
  15 #include <arpa/inet.h>
  16
  17 #define PORT "3490" // the port client will be connecting to
  18
  19 #define MAXDATASIZE 100 // max number of bytes we can get at once
  20
  21 // get sockaddr, IPv4 or IPv6:
  22 void *get_in_addr(struct sockaddr *sa)
  23 {
  24         if (sa->sa_family == AF_INET) {
  25                 return &(((struct sockaddr_in*)sa)->sin_addr);
  26         }
  27
  28         return &(((struct sockaddr_in6*)sa)->sin6_addr);
  29 }
  30
  31 int main(int argc, char *argv[])
  32 {
  33         int sockfd, numbytes;
  34         char buf[MAXDATASIZE];
  35         struct addrinfo hints, *servinfo, *p;
  36         int rv;
  37         char s[INET6_ADDRSTRLEN];
  38
  39         if (argc != 2) {
  40             fprintf(stderr,"usage: client hostname\n");
  41             exit(1);
  42         }
  43
  44         memset(&hints, 0, sizeof hints);
  45         hints.ai_family = AF_UNSPEC;
  46         hints.ai_socktype = SOCK_STREAM;
  47
  48         if ((rv = getaddrinfo(argv[1], PORT, &hints, &servinfo)) != 0) {
  49                 fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
  50                 return 1;
  51         }
  52
  53         // loop through all the results and connect to the first we can
  54         for(p = servinfo; p != NULL; p = p->ai_next) {
  55                 if ((sockfd = socket(p->ai_family, p->ai_socktype,
  56                                 p->ai_protocol)) == -1) {
  57                         perror("client: socket");
  58                         continue;
  59                 }
  60
  61                 if (connect(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
  62                         close(sockfd);
  63                         perror("client: connect");
  64                         continue;
  65                 }
  66
  67                 break;
  68         }
  69
  70         if (p == NULL) {
  71                 fprintf(stderr, "client: failed to connect\n");
  72                 return 2;
  73         }
  74
  75         inet_ntop(p->ai_family, get_in_addr((struct sockaddr *)p->ai_addr),
  76                         s, sizeof s);
  77         printf("client: connecting to %s\n", s);
  78
  79         freeaddrinfo(servinfo); // all done with this structure
  80
  81         if ((numbytes = recv(sockfd, buf, MAXDATASIZE-1, 0)) == -1) {
  82             perror("recv");
  83             exit(1);
  84         }
  85
  86         buf[numbytes] = '\0';
  87
  88         printf("client: received '%s'\n",buf);
  89
  90         close(sockfd);
  91
  92         return 0;
  93 }
  94