7.3.12 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);
}