8.5 UDP Echo Client: main Function

The UDP client main function is shown in Figure 8.7.

Figure 8.7 UDP echo client.

udpcliserv/udpcli01.c

 1 #include     "unp.h"

 2 int
 3 main(int argc, char **argv)
 4 {
 5     int     sockfd;
 6     struct sockaddr_in servaddr;

 7     if(argc != 2)
 8        err_quit("usage: udpcli <IPaddress>");

 9     bzero(&servaddr, sizeof(servaddr));
10     servaddr.sin_family = AF_INET;
11     servaddr.sin_port = htons(SERV_PORT);
12     Inet_pton(AF_INET, argv[1], &servaddr.sin_addr);

13     sockfd = Socket(AF_INET, SOCK_DGRAM, 0);

14     dg_cli(stdin, sockfd, (SA *) &servaddr, sizeof(servaddr));

15     exit(0);
16 }

Fill in socket address structure with server's address

9–12 An IPv4 socket address structure is filled in with the IP address and port number of the server. This structure will be passed to dg_cli, specifying where to send datagrams.

13–14 A UDP socket is created and the function dg_cli is called.