Windows下网络编程及多线程模型

Socket编程

要想客户端和服务器能在网络中通信，那必须得使用 Socket 编程。

服务端首先调用 socket() 函数，创建网络协议为 IPv4，以及传输协议为 TCP 的 Socket ，接着调用 bind() 函数，给这个 Socket 绑定一个 IP 地址和端口。然后，服务端可以调用 listen() 函数进行监听，进入了监听状态后，通过调用 accept() 函数，来从内核获取客户端的连接，如果没有客户端连接，则会阻塞等待客户端连接的到来。

客户端在创建好 Socket 后，调用 connect() 函数发起连接，该函数的参数要指明服务端的 IP 地址和端口号，接着就是开始三次握手。

在 TCP 连接的过程中，服务器的内核实际上为每个 Socket 维护了两个队列：

• 半连接队列
• 全连接队列

当 TCP 全连接队列不为空后，服务端的 accept() 函数，就会从内核中的 TCP 全连接队列里拿出一个已经完成连接的 Socket 返回应用程序，后续数据传输都用这个 Socket。因此，进行三次握手的Socket和传输数据的Socket是不一样的。

连接建立后，客户端和服务端就开始相互传输数据了，双方都可以通过 read() 和 write() 函数来读写数据。

下面看一下同步阻塞的方式实现的Socket通信。将两份cpp文件放在不同工程中，分别生成。

server.cpp

#include <stdio.h>
#include <windows.h>

#pragma comment(lib, "ws2_32.lib")

int main()
{
	//1. 请求协议版本
	WSADATA wsaData;
	WSAStartup(MAKEWORD(2, 2), &wsaData);
	if (LOBYTE(wsaData.wVersion) != 2 || HIBYTE(wsaData.wVersion) != 2) {
		printf("request failed!\n");
		return -1;
	}
	printf("request protocol success!\n");

	//2. 创建Socket
	SOCKET serverSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
	if (serverSocket == SOCKET_ERROR) {
		printf("create failed!\n");
		WSACleanup();
		return -2;
	}
	printf("create socket success!\n");

	//3.创建协议族
	SOCKADDR_IN addr = { 0 };
	addr.sin_family = AF_INET; //协议版本
	addr.sin_addr.S_un.S_addr = inet_addr("192.168.1.127");
	addr.sin_port = htons(10086);//0-65535 10000左右

	//4.绑定
	int r = bind(serverSocket, (sockaddr*)&addr, sizeof addr);
	if (-1 == r) {
		printf("bind failed!\n");
		closesocket(serverSocket);
		WSACleanup();
		return -2;
	}
	printf("bind success!\n");

	//5.监听
	r = listen(serverSocket, 10);
	if (-1 == r) {
		printf("listen failed!\n");
		closesocket(serverSocket);
		WSACleanup();
		return -2;
	}
	printf("listen success!\n");

	//6.等待客户端连接    阻塞   
	SOCKADDR_IN cAddr = { 0 };
	int len = sizeof(cAddr);
	SOCKET clientSocket = accept(serverSocket, (sockaddr*)&cAddr, &len);
	if (SOCKET_ERROR == clientSocket) {
		printf("serverd failed!\n");
		closesocket(clientSocket);
		WSACleanup();
		return -2;
	}
	printf("one client(%s) has connected server!\n", inet_ntoa(cAddr.sin_addr));

	//7.通信
	char buff[1024];
	while (1) {
		r = recv(clientSocket, buff, 1023, NULL);
		if (r > 0) {
			buff[r] = 0; // 添加'\0'
			printf(">>%s\n", buff);
		}
	}
	return 0;
}

client.cpp

#include <stdio.h>
#include <windows.h>

#pragma comment(lib, "ws2_32.lib")

int main()
{
	//1. 请求协议版本
	WSADATA wsaData;
	WSAStartup(MAKEWORD(2, 2), &wsaData);
	if (LOBYTE(wsaData.wVersion) != 2 || HIBYTE(wsaData.wVersion) != 2) {
		printf("request failed!\n");
		return -1;
	}
	printf("request protocol success!\n");

	//2. 创建Socket
	SOCKET clientSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
	if (clientSocket == SOCKET_ERROR) {
		printf("create failed!\n");
		WSACleanup();
		return -2;
	}
	printf("create socket success!\n");

	//3.获取服务器协议族
	SOCKADDR_IN addr = { 0 };
	addr.sin_family = AF_INET; //协议版本
	addr.sin_addr.S_un.S_addr = inet_addr("192.168.1.127");
	addr.sin_port = htons(10086);//0-65535 10000左右

	//4.连接服务器
	int r = connect(clientSocket, (sockaddr*)&addr, sizeof addr);
	if (r == -1) {
		printf("connecting server failed!\n");
		return -1;
	}
	printf("connecting server success!\n");

	//5.通信
	char buff[1024];
	while (1) {
		memset(buff, 0, 1024);
		printf("please enter your words: ");
		gets_s(buff);
		r = send(clientSocket, buff, strlen(buff), NULL);
	}

	return 0;
}

通信效果

多线程模型

同步阻塞的方式只能让服务器服务一个客户端，当服务器没有结束当前客户端的网络I/O时，其他客户端是无法连接服务器的。因此，我们可以使用多线程模型来处理多客户端的请求。

server.cpp

#include <stdio.h>
#include <windows.h>

#pragma comment(lib, "ws2_32.lib")

SOCKADDR_IN cAddr = { 0 };
int len = sizeof(cAddr);
SOCKET clientSocket[1024];
int count = 0;

void communication(int idx) {
	char buff[1024];
	int r;
	while (1) {
		r = recv(clientSocket[idx], buff, 1023, NULL);
		if (r > 0) {
			buff[r] = 0;
			printf("%d:%s\n", idx, buff);
			//广播数据
			for (int i = 0; i < count; i++) {
				send(clientSocket[i], buff, strlen(buff), NULL);
			}
		}
	}
}

int main()
{
	//1. 请求协议版本
	WSADATA wsaData;
	WSAStartup(MAKEWORD(2, 2), &wsaData);
	if (LOBYTE(wsaData.wVersion) != 2 || HIBYTE(wsaData.wVersion) != 2) {
		printf("request failed!\n");
		return -1;
	}
	printf("request protocol success!\n");

	//2. 创建Socket
	SOCKET serverSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
	if (serverSocket == SOCKET_ERROR) {
		printf("create failed!\n");
		WSACleanup();
		return -2;
	}
	printf("create socket success!\n");

	//3.创建协议族
	SOCKADDR_IN addr = { 0 };
	addr.sin_family = AF_INET; //协议版本
	addr.sin_addr.S_un.S_addr = inet_addr("192.168.1.127");
	addr.sin_port = htons(10086);//0-65535 10000左右

	//4.绑定
	int r = bind(serverSocket, (sockaddr*)&addr, sizeof addr);
	if (-1 == r) {
		printf("bind failed!\n");
		closesocket(serverSocket);
		WSACleanup();
		return -2;
	}
	printf("bind success!\n");

	//5.监听
	r = listen(serverSocket, 10);
	if (-1 == r) {
		printf("listen failed!\n");
		closesocket(serverSocket);
		WSACleanup();
		return -2;
	}
	printf("listen success!\n");

	//6.等待客户端连接    阻塞   
	while (1) {
		clientSocket[count] = accept(serverSocket, (sockaddr*)&cAddr, &len);
		if (SOCKET_ERROR == clientSocket[count]) {
			printf("serverd failed!\n");
			closesocket(serverSocket);
			WSACleanup();
			return -2;
		}
		printf("one client(%s) has connected server!\n", inet_ntoa(cAddr.sin_addr));

		CreateThread(NULL, NULL, (LPTHREAD_START_ROUTINE)communication, (char*)count, NULL, NULL);
		count++;
	}

	//7.通信
	char buff[1024];
	while (1) {
		r = recv(clientSocket[count], buff, 1023, NULL);
		if (r > 0) {
			buff[r] = 0; // 添加'\0'
			printf(">>%s\n", buff);
		}
	}
	return 0;
}

client.cpp

#include <stdio.h>

#include <graphics.h> //easyX

#pragma comment(lib, "ws2_32.lib")

SOCKET clientSocket;
HWND hWnd;

int count = 0;

void received() {
	char recvBuff[1024];
	int r;
	while (1) {
		r = recv(clientSocket, recvBuff, 1023, NULL);
		if (r > 0) {
			recvBuff[r] = 0;
			outtextxy(0, count * 20, recvBuff);
			count++;
		}
	}
}

int main()
{
	initgraph(300, 400, SHOWCONSOLE);

	//1. 请求协议版本
	WSADATA wsaData;
	WSAStartup(MAKEWORD(2, 2), &wsaData);
	if (LOBYTE(wsaData.wVersion) != 2 || HIBYTE(wsaData.wVersion) != 2) {
		printf("request failed!\n");
		return -1;
	}
	printf("request protocol success!\n");

	//2. 创建Socket
	clientSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
	if (clientSocket == SOCKET_ERROR) {
		printf("create failed!\n");
		WSACleanup();
		return -2;
	}
	printf("create socket success!\n");

	//3.获取服务器协议族
	SOCKADDR_IN addr = { 0 };
	addr.sin_family = AF_INET; //协议版本
	addr.sin_addr.S_un.S_addr = inet_addr("192.168.1.127");
	addr.sin_port = htons(10086);//0-65535 10000左右

	//4.连接服务器
	int r = connect(clientSocket, (sockaddr*)&addr, sizeof addr);
	if (r == -1) {
		printf("connecting server failed!\n");
		return -1;
	}
	printf("connecting server success!\n");

	//5.通信
	char buff[1024];
	CreateThread(NULL, NULL, (LPTHREAD_START_ROUTINE)received, NULL, NULL, NULL);
	while (1) {
		memset(buff, 0, 1024);
		printf("please enter your words: ");
		gets_s(buff);
		r = send(clientSocket, buff, strlen(buff), NULL);
	}

	return 0;
}

参考文献

1. Windows网络编程， socket开发
2. I/O多路复用