linux TCP socket 通信demo

1. server.c：

   #include <sys/socket.h>
   #include <netinet/in.h>
   #include <arpa/inet.h>
   #include <unistd.h>
   #include <stdlib.h>
   #include <assert.h>
   #include <stdio.h>
   #include <string.h>
   #include <errno.h>
   
   
   int main(int argc,char* argv[])
   {
   	printf("server start up\n");
   
   	if(argc <= 3)
   	{
   			printf("usage:%s ip port backlog\n",basename(argv[0]));
   			return 1;
   	}
   
   	//IP地址
   	const char* ip = argv[1];
   	//端口号
   	int port = atoi(argv[2]);
   	//内核监听队列的最大长度（完全连接的socket）
   	int backlog = atoi(argv[3]);
   
   	//创建socket	(TIP/IP协议族，流式socket)
   	int server_sockfd = socket(PF_INET,SOCK_STREAM,0);
   
   	//TCP/IP协议族的socket地址结构体
   	struct sockaddr_in server_addr;
   	bzero(&server_addr,sizeof(server_addr));
   	server_addr.sin_family = AF_INET;			//TCP/IPv4的地址族
   	inet_pton(AF_INET,ip,&server_addr.sin_addr);		//将IP地址字符串转换为二进制的整数并赋给addr.sin_server_addr
   	server_addr.sin_port = htons(port);			//端口，host to net，将主机字节序（小端）转换为网络字节序（大端）
   
   	//将文件描述符sock和socket地址关联，仅服务端需要，客户端自动绑定地址
   	//注意需要强制转换为 struct sockaddr*
   	int ret = bind(server_sockfd,(struct sockaddr*)&server_addr,sizeof(server_addr));
   	assert(ret != -1);
   
   	//监听
   	ret = listen(server_sockfd,backlog);
   	assert(ret != -1);
   
   	//等待客户端做些连接等相关工作
   	sleep(5);	
   
   	//客户端地址信息
   	struct sockaddr_in client_addr;
   	socklen_t client_addr_addrlength = sizeof(client_addr);
   
   	//接受连接,并将被接受的远端sock地址信息保存在第二个参数中
   	int client_addr_sockfd = accept(server_sockfd,(struct sockaddr*)&client_addr,&client_addr_addrlength);
   
   	if(client_addr_sockfd < 0)
   	{
   		printf("errno is:%d\n",errno);
   		return -1;
   	}
   	else
   	{
   		//inet_ntoa(struct addr_in) 将IP地址转换为字符串并返回
   		//只是从监听队列中取出连接，即使客户端已经断开网络连接也会accept成功
   		printf("accept client_addr %s\n",inet_ntoa(client_addr.sin_addr));
   	}
   
   	int len;
   	char buf[128];
   	strcpy(buf,"Welcome to my server\n");
   	//send: TCP数据发送接口
   	len = send(client_addr_sockfd,buf,strlen(buf),0);//发送欢迎信息  
   
   	//recv: TCP数据接收接口，返回值为实际接收到的字节数，可能小于设定值，所以需要多次recv才能读到完整数据
   	memset(buf,0,sizeof(buf));
   	while((len = recv(client_addr_sockfd,buf,128,0)) > 0)
   	{
   		buf[len]='\0';
   		printf("%s\n",buf);
   
   		printf("Enter string to send:");
   		scanf("%s",buf);
   
   		//输入“quit”退出
   		if(!strcmp(buf,"quit"))
   		{
   			break;
   		}
   
   		if(send(client_addr_sockfd,buf,len,0) < 0)
   		{
   			
   			return -1;			
   		}
   	}
   
   	//关闭连接，实际只是socket的引用-1,必须引用为0才会真正关闭
   	close(client_addr_sockfd);
   	close(server_sockfd);
   	return 0;
   }
   
   
   

2. client.c ：

   #include <sys/socket.h>
   #include <netinet/in.h>
   #include <arpa/inet.h>
   #include <signal.h>
   #include <unistd.h>
   #include <stdlib.h>
   #include <assert.h>
   #include <stdio.h>
   #include <string.h>
   #include <errno.h>
   
   int main(int argc,char* argv[])
   {
   	if(argc <= 3)
   	{
   			printf("usage:%s ip port backlog\n",basename(argv[0]));
   			return 1;
   	}
   
   	const char* ip = argv[1];
   	int port = atoi(argv[2]);
   	int backlog = atoi(argv[3]);
   
   	struct sockaddr_in remote_addr;
   	bzero(&remote_addr,sizeof(remote_addr));
   	remote_addr.sin_family = AF_INET;
   	inet_pton(AF_INET,ip,&remote_addr.sin_addr);
   	remote_addr.sin_port = htons(port);
   
   	int remote_sockfd = socket(PF_INET,SOCK_STREAM,0);
   
   	//连接
   	if(connect(remote_sockfd,(struct sockaddr*)&remote_addr,sizeof(struct sockaddr)) < 0)
   	{
   		printf("connect failed\n");
   		return -1;
   	}
   
   	printf("connect success\n");
   	int len = 0;
   	char buf[128];
   	len = recv(remote_sockfd,buf,21,0);
   	buf[len] = '\0';
   	printf("%s",buf);
   
   	while(1)
   	{
   		printf("Enter string to send:");
   		scanf("%s",buf);
   		if(!strcmp(buf,"quit"))
   		{
   			break;
   		}
   		send(remote_sockfd,buf,strlen(buf),0);
   		len = recv(remote_sockfd,buf,128,0);
   		buf[len] = '\0';
   		printf("received:%s\n",buf);
   	}
   
   }