5.4 TCP Echo Client: main Function

5.4 TCP Echo Client: main Function

Figure 5.4 shows the TCP client main function.

Figure 5.3 str_echo function: echoes data on a socket.

lib/str_echo.c

 1 #include    "unp.h"  2 void  3 str_echo(int sockfd)  4 {  5     ssize_t n;  6     char    buf[MAXLINE];  7   again:  8     while ( (n = read(sockfd, buf, MAXLINE)) > 0)  9         Writen(sockfd, buf, n); 10     if (n < 0 && errno == EINTR) 11         goto again; 12     else if (n < 0) 13         err_sys("str_echo: read error"); 14 } 

Figure 5.4 TCP echo client.

tcpcliserv/tcpli01.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: tcpcli <IPaddress>");  9     sockfd = Socket(AF_INET, SOCK_STREAM, 0); 10     bzero(&servaddr, sizeof(servaddr)); 11     servaddr.sin_family = AF_INET; 12     servaddr.sin_port = htons(SERV_PORT); 13     Inet_pton(AF_INET, argv[1], &servaddr.sin_addr); 14     Connect(sockfd, (SA *) &servaddr, sizeof(servaddr)); 15     str_cli(stdin, sockfd);     /* do it all */ 16     exit(0); 17 } 

Create socket, fill in Internet socket address structure

9 “13 A TCP socket is created and an Internet socket address structure is filled in with the server's IP address and port number. We take the server's IP address from the command-line argument and the server's well-known port ( SERV_PORT ) is from our unp.h header.

Connect to server

14 “15 connect establishes the connection with the server. The function str_cli (Figure 5.5) handles the rest of the client processing.