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7.1.13 Helper functions for TCP connections

Those helper function abstract away TCP connection handling from the other examples. It is required to build some examples.

/* This example code is placed in the public domain. */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <unistd.h>

/* tcp.c */
int tcp_connect(void);
void tcp_close(int sd);

/* Connects to the peer and returns a socket
 * descriptor.
 */
extern int tcp_connect(void)
{
        const char *PORT = "5556";
        const char *SERVER = "127.0.0.1";
        int err, sd;
        struct sockaddr_in sa;

        /* connects to server
         */
        sd = socket(AF_INET, SOCK_STREAM, 0);

        memset(&sa, '\0', sizeof(sa));
        sa.sin_family = AF_INET;
        sa.sin_port = htons(atoi(PORT));
        inet_pton(AF_INET, SERVER, &sa.sin_addr);

        err = connect(sd, (struct sockaddr *) &sa, sizeof(sa));
        if (err < 0) {
                fprintf(stderr, "Connect error\n");
                exit(1);
        }

        return sd;
}

/* closes the given socket descriptor.
 */
extern void tcp_close(int sd)
{
        shutdown(sd, SHUT_RDWR);        /* no more receptions */
        close(sd);
}