The Linux Programming Interface

1258 Chapter 61

Listing 61-2: A client for the echo service

––––––––––––––––––––––––––––––––––––––––––––––––––––––sockets/is_echo_cl.c

#include "inet_sockets.h"

#include "tlpi_hdr.h"

#define BUF_SIZE 100

int

main(int argc, char *argv[])

{

int sfd;

ssize_t numRead;

char buf[BUF_SIZE];

if (argc != 2 || strcmp(argv[1], "--help") == 0)

usageErr("%s host\n", argv[0]);

sfd = inetConnect(argv[1], "echo", SOCK_STREAM);

if (sfd == -1)

errExit("inetConnect");

switch (fork()) {

case -1:

errExit("fork");

case 0: /* Child: read server's response, echo on stdout */

for (;;) {

numRead = read(sfd, buf, BUF_SIZE);

if (numRead <= 0) /* Exit on EOF or error */

break;

printf("%.*s", (int) numRead, buf);

}

exit(EXIT_SUCCESS);

default: /* Parent: write contents of stdin to socket */

for (;;) {

numRead = read(STDIN_FILENO, buf, BUF_SIZE);

if (numRead <= 0) /* Exit loop on EOF or error */

break;

if (write(sfd, buf, numRead) != numRead)

fatal("write() failed");

}

/* Close writing channel, so server sees EOF */

if (shutdown(sfd, SHUT_WR) == -1)

errExit("shutdown");

exit(EXIT_SUCCESS);

}

}

––––––––––––––––––––––––––––––––––––––––––––––––––––––sockets/is_echo_cl.c