嵌入式（TCP编程）

TCP编程API

1、socket（）函数

参数：

2、 bind（）函数



如果是IPV6的编程，要使用 struct sockddr_in6结构体（man 7 ipv6），通常更通用的方法可以通过struct sockaddr_storage来编程
3、listen（）函数

参数：
sockfd： 通过socket（）函数拿到的fd
backlog：一般填5

服务器

#include "net.h"

int main (void)
{

	int fd = -1;
	struct sockaddr_in sin;

	/* 1. 创建socket fd */
	if ((fd = socket (AF_INET, SOCK_STREAM, 0)) < 0) {
		perror ("socket");
		exit (1);
	}

	/*2. 绑定 */
	/*2.1 填充struct sockaddr_in结构体变量 */
	bzero (&sin, sizeof (sin));
	sin.sin_family = AF_INET;
	sin.sin_port = htons (SERV_ PORT);	//网络字节序的端口号

	/*优化1: 让服务器程序能绑定在任意的IP上 */
#if 1
	sin.sin_addr.s_addr = htonl (INADDY_ANY);
#else
	if (inet_pton (AF_INET, SERV_IP_ADDR, (void *) &sin.sin_addr) != 1) {
		perror ("inet_pton");
		exit (1);
	}
#endif
	/*2.2 绑定 */
	if (bind (fd, (struct sockaddr *) &sin, sizeof (sin)) < 0) {
		perror ("bind");
		exit (1);
	}

	/*3. 调用listen()把主动套接字变成被动套接字 */
	if (listen (fd, BACKLOG) < 0) {
		perror ("listen");
		exit (1);
	}
	printf ("Server starting....OK!\n");
	int newfd = -1;
	/*4. 阻塞等待客户端连接请求 */
#if 0
	newfd = accept (fd, NULL, NULL);
	if (newfd < 0) {
		perror ("accept");
		exit (1);
	}
#else
	/*优化2：通过程序获取刚建立连接的socket的客户端的IP地址和端口号 */
	struct sockaddr_in cin;
	socklen_t addrlen = sizeof (cin);
	if ((newfd = accept (fd, (struct sockaddr *) &cin, &addrlen)) < 0) {
		perror ("accept");
		exit (1);
	}

	char ipv4_addr[16];
	if (!inet_ntop (AF_INET, (void *) &cin.sin_addr, ipv4_addr, sizeof (cin))) {
		perror ("inet_ntop");
		exit (1);
	}

	printf ("Clinet(%s:%d) is connected!\n", ipv4_addr, ntons (cin.sin_port));

#endif
	/*5. 读写 */
	//..和newfd进行数据读写
	int ret = -1;
	char buf[BUFSIZ];
	while (1) {
		bzero (buf, BUFSIZ);
		do {
			ret = read (newfd, buf, BUFSIZ - 1);
		} while (ret < 0 && EINTR == errno);
		if (ret < 0) {

			perror ("read");
			exit (1);
		}
		if (!ret) {				//对方已经关闭
			break;
		}
		printf ("Receive data: %s\n", buf);

		if (!strncasecmp (buf, QUIT_STR, strlen (QUIT_STR))) {	//用户输入了quit字符
			printf ("Client is exiting!\n");
			break;
		}
	}
	close (newfd);

	close (fd);
	return 0;
}

客户端

#include "net.h"

int main (void)
{
	int fd = -1;
	struct sockaddr_in sin;
	/* 1. 创建socket fd */
	if ((fd = socket (AF_INET, SOCK_STREAM, 0)) < 0) {
		perror ("socket");
		exit (1);
	}
	/*2.连接服务器 */

	/*2.1 填充struct sockaddr_in结构体变量 */
	bzero (&sin, sizeof (sin));

	sin.sin_family = AF_INET;
	sin.sin_port = htons (SERV_PORT);	//网络字节序的端口号
#if 0
	sin.sin_addr.s_addr = inet_addr (SERV_IP_ADDR);
#else
	if (inet_pton (AF_INET, SERV_IP_ADDR, (void *) &sin.sin_addr) != 1) {
		perror ("inet_pton");
		exit (1);
	}
#endif

	if (connect (fd, (struct sockaddr *) &sin, sizeof (sin)) < 0) {
		perror ("connect");
		exit (1);
	}

	printf ("Client staring...OK!\n");
	/*3. 读写数据 */
	char buf[BUFSIZ];
	int ret = -1;
	while (1) {
		bzero (buf, BUFSIZ);
		if (fgets (buf, BUFSIZ - 1, stdin) == NULL) {
			continue;
		}
		do {
			ret = write (fd, buf, strlen (buf));
		} while (ret < 0 && EINTR == errno);

		if (!strncasecmp (buf, QUIT_STR, strlen (QUIT_STR))) {	//用户输入了quit字符
			printf ("Client is exiting!\n");
			break;
		}
	}

	/*4.关闭套接字 */
	close (fd);
}

net.h

#ifndef __MAKEU_NET_H__
#define __MAKEU_NET_H__

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <stdlib.h>
#include <strings.h>
#include <sys/types.h>			/* See NOTES */
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h>			/* superset of previous */

#define SERV_PORT 5001
#define SERV_IP_ADDR "192.168.7.246"
#define BACKLOG 5

#define QUIT_STR "quit"

#endif