C++Socket编程—TCP通信

一.TCP协议

传输控制协议（TCP，Transmission Control Protocol）是一种面向连接的、可靠的、基于字节流的传输层通信协议。

TCP通过校验和、序列号、确认应答、重发控制、连接管理以及窗口控制等机制实现可靠性传输。

udp -无连接（可不确认进行直接发送）
tcp -面向连接（必须经过双方确认）

2.TCP协议创建过程

1）创建socket
2）绑定端口
3）监听（转给另外一个socket）
4）接受连接
5）收发数据

3.代码实例—TCP通信，服务器可以接受客户端发来的信息

服务器：

        //1.创建TCP socket
	SOCKET sockServer = socket(AF_INET,
		SOCK_STREAM,
		IPPROTO_TCP
	);
	//2.绑定端口
	sockaddr_in siServer;
	siServer.sin_family = AF_INET;
	siServer.sin_port = htons(8888);
	siServer.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");
	int nRet = bind(sockServer, (sockaddr*)&siServer, sizeof(siServer));
	if (nRet == SOCKET_ERROR)
	{
		printf("端口绑定失败\n");
		return 0;
	}
	//3.监听
	nRet = listen(sockServer, SOMAXCONN);//监听最大值
	if (nRet == SOCKET_ERROR)
	{
		printf("监听失败\n");
		return 0;
	}
	//4.接受连接
	while (true)
		{
			// 	4) 接受连接
			sockaddr_in siClient;
			int nSize = sizeof(siClient);
			SOCKET sockClient = accept(sockServer, (sockaddr*)&siClient, &nSize);
			if (sockClient == SOCKET_ERROR)
			{
				printf("接受连接失败 \r\n");
				return 0;
			}
			printf("IP:%s port:%d 连接到服务器. \r\n",
				inet_ntoa(siClient.sin_addr),
				ntohs(siClient.sin_port));
	
			HANDLE hTread = CreateThread(NULL, 0, HandleClientThread, (LPVOID)sockClient, 0, NULL);//用来收发数据的线程
			CloseHandle(hTread);
		}
		
		
//5.创建一个线程用来收发数据
DWORD WINAPI HandleClientThread(LPVOID pParam)
{
	SOCKET sockClient = (SOCKET)pParam;

	while (TRUE)
	{
		//5) 收发数据
		char aryBuff[MAXWORD] = { 0 };
		int nRet = recv(sockClient, aryBuff, sizeof(aryBuff), 0);
		if (nRet == 0 || nRet == SOCKET_ERROR)
		{
			printf("接受数据失败 \r\n");
			return 0;
		}
		printf("收到数据: %s \r\n", aryBuff);

		char szBuff[] = { "recv OK \r\n" };
		nRet = send(sockClient, szBuff, sizeof(szBuff), 0);
		if (nRet == SOCKET_ERROR)
		{
			printf("数据发送失败 \r\n");
			return 0;
		}
	}

	return 0;
}

 客户端：

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	//1.创建TCP socket
	SOCKET sockClient = socket(AF_INET,
		SOCK_STREAM,
		IPPROTO_TCP
	);

	//2.连接服务器
	sockaddr_in siServer;
	siServer.sin_family = AF_INET;
	siServer.sin_port = htons(8888);
	siServer.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");
	int nRet = connect(sockClient, (sockaddr*)&siServer, sizeof(siServer));
	if (nRet == SOCKET_ERROR)
	{
		printf("服务器连接失败");
	}
	//3.收发数据
	while (TRUE)
	{
		
		char szBuff[MAXWORD] = { 0 };
		cin >> szBuff;

		nRet = send(sockClient, szBuff, sizeof(szBuff), 0);
		if (nRet == SOCKET_ERROR)
		{
			printf("数据发送失败 \r\n");
			return 0;
		}

		char aryBuff[MAXWORD] = { 0 };
		nRet = recv(sockClient, aryBuff, sizeof(aryBuff), 0);
		if (nRet == 0 || nRet == SOCKET_ERROR)
		{
			printf("接受数据失败 \r\n");
			return 0;
		}
		printf("收到数据: %s \r\n", aryBuff);
	}


	closesocket(sockClient);
	return 0;