Simple echo server: Refactor #2: Move the work loop into its own function.

echo-server-2.c

/**
 * Simple echo server
 *
 * This program listens for connections on the
 * loopback interface, on port 9999. Upon connecting,
 * The first line we read, of up to BUF_LEN bytes, is
 * then sent back to the sender, and the connection
 * is closed.
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

#define BUF_LEN 25
static char buf[BUF_LEN + 1];

/**
 * Read data from the given file descriptor,
 * and echo it back out.
 */
static void handle_connection(int fd)
{
	int i;
	unsigned int bytes_read = 0;

	/**
	 * Read data until the buffer is full, we get an EOF, or
	 * we've read a '\n'.
	 */
	while (bytes_read < BUF_LEN) {
		i = recv(fd, buf + bytes_read, BUF_LEN - bytes_read, 0);
		if (!i) break;

		if (i < 0) {
			if (errno == EINTR)
				continue;
			perror("recv");
			return;
		}

		bytes_read += i;
		if (strchr(buf, '\n')) break;
	}

	/* Echo data if we got it */
	if (bytes_read) {
		buf[bytes_read + 1] = 0;
		printf("Read: %s\n", buf);

		if (send(fd, buf, bytes_read, 0) < 0)
			perror("send");
	}
}

int main(int argc, char *argv[])
{
	int fd, c_fd, i=1;
	struct sockaddr_in sa;

	/* Open a TCP socket */
	if ((fd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0) {
		perror("socket");
		return EXIT_FAILURE;
	}

	/* Let's ensure we can reuse our address */
	setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &i, sizeof(int));

	/* This will bind to localhost:9999 */
	memset(&sa, 0, sizeof(sa));
	sa.sin_family      = AF_INET;
	sa.sin_port        = htons(9999);
	sa.sin_addr.s_addr = htonl(INADDR_LOOPBACK);

	if (bind(fd, (struct sockaddr *)&sa, sizeof(sa)) < 0) {
		perror("bind");
		close(fd);
		return EXIT_FAILURE;
	}

	/* Listen for one connection at a time */
	if (listen(fd, 1) < 0) {
		perror("listen");
		close(fd);
		return EXIT_FAILURE;
	}

	while (1) {
		/* Clear the buffer */
		memset(buf, 0, BUF_LEN+1);

		if ((c_fd = accept(fd, NULL, NULL)) < 0) {
			perror("accept");
			break;
		}

		/* We've got a live one. */
		printf("Got connection\n");
		handle_connection(c_fd);
		close(c_fd);
	}

	if (c_fd) close(c_fd);
	close(fd);
	return EXIT_SUCCESS;
}