client_udp.c

   1 /* UDP client in the internet domain */
   2 #include <sys/types.h>
   3 #include <sys/socket.h>
   4 #include <netinet/in.h>
   5 #include <arpa/inet.h>
   6 #include <netdb.h>
   7 #include <stdio.h>
   8 #include <stdlib.h>
   9 #include <unistd.h>
  10 #include <string.h>
  11
  12 void error(const char *);
  13 int main(int argc, char *argv[])
  14 {
  15    int sock, n;
  16    unsigned int length;
  17    struct sockaddr_in server, from;
  18    struct hostent *hp;
  19    char buffer[256];
  20
  21    if (argc != 3) { printf("Usage: server port\n");
  22                     exit(1);
  23    }
  24    sock= socket(AF_INET, SOCK_DGRAM, 0);
  25    if (sock < 0) error("socket");
  26
  27    server.sin_family = AF_INET;
  28    hp = gethostbyname(argv[1]);
  29    if (hp==0) error("Unknown host");
  30
  31    bcopy((char *)hp->h_addr,
  32         (char *)&server.sin_addr,
  33          hp->h_length);
  34    server.sin_port = htons(atoi(argv[2]));
  35    length=sizeof(struct sockaddr_in);
  36    printf("Please enter the message: ");
  37    while(1){
  38            bzero(buffer,256);
  39            fgets(buffer,255,stdin);
  40            n=sendto(sock,buffer,
  41                            strlen(buffer),0,(const struct sockaddr *)&server,length);
  42            if (n < 0) error("Sendto");
  43            n = recvfrom(sock,buffer,256,0,(struct sockaddr *)&from, &length);
  44            if (n < 0) error("recvfrom");
  45            write(1,"Got an ack: ",12);
  46            write(1,buffer,n);
  47    }
  48    close(sock);
  49    return 0;
  50 }
  51
  52 void error(const char *msg)
  53 {
  54     perror(msg);
  55     exit(0);
  56 }