[网络协议]应用开发基础----网络编程(TCP)

server:

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

/*socket
*bind
*listen
*accept
*send/recv
*/
#define PORT 8888  //端口号设为8888
#define backlog 10
int main(int argc,char **argv)
{

	int serverfd;
	int clientfd;
	int ret;
	int addrlen;
	struct sockaddr_in s_addr;
	struct sockaddr_in c_addr;
	int clientnum = 0;


	unsigned char recvbuf[1000];
	int recvlen;

	serverfd = socket(AF_INET, SOCK_STREAM, 0);
	if(serverfd == -1)
	{
		printf("socket error\n");
		return -1;
	}
	/* 填充服务器端口地址信息，以便下面使用此地址和端口监听 */
	s_addr.sin_family = AF_INET;
	s_addr.sin_port = htons(PORT);
	s_addr.sin_addr.s_addr = INADDR_ANY;
	memset(s_addr.sin_zero,0,8);
	/* 使用bind进行绑定端口 */  
	ret = bind(serverfd, (const struct sockaddr *)&s_addr,sizeof(struct sockaddr));
	if(ret ==-1 )
	{
		printf("bind error\n");
		return -1;
	}
	/* 开始监听相应的端口 */  
	ret = listen(serverfd, backlog);
	if(ret == -1)
	{
		printf("listen error\n");
		return -1;
	}
	printf("waiting client connect......\n");
	while(1)
	{
		addrlen = sizeof(struct sockaddr);
	/* accept服务端使用函数，调用时即进入阻塞状态，等待用户进行连接，在没有客户端进行连接时，程序停止在此处， 
   此处accept的第二个参数用于获取客户端的端口和地址信息。 
    */ 
		clientfd = accept(serverfd, (struct sockaddr *)&c_addr, &addrlen);
		clientnum++;
		if(clientfd != -1)
		{
			printf("connect client success: %d , %s \n",clientnum,inet_ntoa(c_addr.sin_addr));
			if(!fork())
			{
			/* 子进程的源码 */
				while(1){
					recvlen = recv(clientfd, recvbuf, 999, 0);
					if(recvlen <= 0){
						printf("recv error\n");
						close(clientfd);
						return -1;
					}else{
						recvbuf[recvlen] = '\0';
						printf("get the msg from client :%s\n",recvbuf);
					}

				}

			}

		}

	}
	close(serverfd);

	return 0;
}

client.c:

#include <stdio.h>
#include <sys/types.h>          /* See NOTES */
#include <sys/socket.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdlib.h>
/*socket
*connect
*send/recv
*/
#define PORT 8888
int main(int argc,char **argv)
{

	int clientfd;
	int ret;
	struct sockaddr_in s_addr;

	unsigned char sendbuf[1000];
	int sendlen;

	if (argc != 2) {
               fprintf(stderr, "%s <dotted-address>\n", argv[0]);
               exit(EXIT_FAILURE);
    }

	clientfd = socket(AF_INET, SOCK_STREAM, 0);
	if(clientfd == -1)
	{
		printf("socket error\n");
		return -1;
	}

	s_addr.sin_family = AF_INET;
	s_addr.sin_port = htons(PORT);
	if (inet_aton(argv[1], &s_addr.sin_addr) == 0) {
        printf("server ip :%s \n",argv[0]);
        return -1;
    }

	memset(s_addr.sin_zero,0,8);
	ret = connect(clientfd, (struct sockaddr * )&s_addr,sizeof(struct sockaddr));
	if(ret ==-1 )
	{
		printf("connect error\n");
		return -1;
	}
	
	printf("connect success!!!\n");
	while(1)
	{
		 if(fgets(sendbuf, 9999, stdin)){
				sendlen = send(clientfd, sendbuf, strlen(sendbuf), 0);
				if(sendlen <= 0){
					printf("send error\n");
					close(clientfd);
					return -1;	
				}
		}
	}
	close(clientfd);
}

htons是将short型数据字节序由主机型转换为网络型，其实就是
将2字节数据的前后两个字节倒换，和对应的ntohs效果、实质相同，只不过名字不同。htonl和ntohl是
操作的4字节整形。将0x12345678变为0x78563412，名字不同，内容两两相同，一般情况下网络为大端，
PPC的cpu为大端，x86的cpu为小端，arm的可以配置大小端，需要保证接收时字节序正确。