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C：TCP协议实现网络通讯

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分成两个项目：服务端和客户端，完整源码在最后

服务端

  1. 包含相关的库文件

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    #include <stdio.h>
    #include <WinSock2.h>//windows网络通讯头文件
    #pragma comment(lib,"ws2_32.lib")//一个库文件(windows不开源) ws2_32,提供接口

  2. 开启网络权限

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    WSADATA wsaData;
    WSAStartup(MAKEWORD(2, 2), &wsaData);

  3. 创建socket套接字

    先看一下socket的数据结构

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    socket(
    	_In_ int af,		//协议地址族 AF_INET/AF_INET6 ipv4/ipv6
    	_In_ int type,		//协议类型 TCP/UDP SOCK_STREAM/SOCK_DGRAM
    	_In_ int protocol	//保护方式
    );

    创建socket，如果创建失败，socket值为-1

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    //创建socket
    SOCKET server_socket = socket(AF_INET, SOCK_STREAM, 0);//如果创建失败为-1
    //进行检查
    if (server_socket == -1) {
    	printf("server socket create failed!Error Code:%d\n", GetLastError());
    	exit(-1);
    }

  4. 指定ip和端口号

    先来看一下struct sockaddr_in的数据结构

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    typedef struct sockaddr_in {
    	short   sin_family;//协议地址族
    	USHORT sin_port;//端口号 5000+
    	IN_ADDR sin_addr;//服务端，所有网卡都要监测，所以一般为0.0.0.0
    					//inet_addr()——将点分十进制的IP地址转换为整数
    	CHAR sin_zero[8];//保留位置 可能将来升级协议可能会用
    } SOCKADDR_IN, * PSOCKADDR_IN;

    这里涉及到大端序和小端序的内容

    • 大端序：数字大的在前面 比如：百 十 个

    • 小端序：数字小的在前面 比如：个 十 百

    例：本地为90 1f 00 00为小端序，网络上为大端序00 00 1f 90（实际值）——8080

    htons()：小端序转换为大端序 eg：htons(8080);

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    struct sockaddr_in local;
    local.sin_family = AF_INET;
    local.sin_port = htons(8080);//将8080转换为大端序
    local.sin_addr.S_un.S_addr = inet_addr("0.0.0.0");

  5. 绑定socket和端口

    bind()

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    // 绑定socket和端口
    if (bind(server_socket, (struct sockaddr*)&local, sizeof(struct sockaddr_in))
    	== -1) {
    	printf("bind server socket failed!Error Code:%ld\n", GetLastError());
    	exit(-1);
    }

  6. 监听端口

    listen()

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    if (listen(server_socket, 10) == -1) {
    	printf("listen server socket failed!Error Code:%ld\n", GetLastError());
    	exit(-1);
    }
    printf("bind and listen success. wait client connect ...\n");

  7. 等待客户端连接

    accept()：函数进行过程就是三次握手

    accept函数是阻塞函数，没有客户端连接就停在这里

    server_socket：负责传话

    返回值：一个新的socket负责通信 

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    SOCKET client_socket = accept(server_socket, NULL, NULL);

  8. 循环处理

    可以接收消息或者发送消息，在循环内部自行定义

    recv()：从通信socket上接收数据

    • 返回值为-1，表示出错
    • 返回值为0，表示正常断开
    • 返回值为正数，表示接收到了多少数据
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    while (1) {
    	char buff[BUFSIZ * 4] = { 0 };//接收数据
        
    	int ret = recv(client_socket, buff, BUFSIZ * 4, 0);
    	if (ret <= 0) break;
        
    	printf("ret:%d buff:%s\n", ret, buff);

    	if (memcmp(buff, "music", strlen("music")) == 0) {
    		//表示当你接收到"music"，进行这部分处理
    		printf("playing music\r\n");
    	}
    }

客户端

  1. 包含相关的库文件

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    #include <stdio.h>
    #include <WinSock2.h>//windows网络通讯头文件
    #pragma comment(lib,"ws2_32.lib")//一个库文件(windows不开源) ws2_32,提供接口

  2. 开启网络权限

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    WSADATA wsaData;
    WSAStartup(MAKEWORD(2, 2), &wsaData);

  3. 创建socket套接字

    跟服务端代码一样

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    //创建socket
    SOCKET client_socket = socket(AF_INET, SOCK_STREAM, 0);
    if (client_socket == -1) {
    	printf("client socket create failed!Error Code:%d\n", GetLastError());
    	exit(-1);
    }

  4. 指定目标ip和端口号

    跟服务端不同的是，不是监听所有，只是针对目标ip

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    struct sockaddr_in target;
    target.sin_family = AF_INET;
    target.sin_port = htons(8080);
    //127.0.0.1本地环回
    //或者填本机ip
    target.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");

  5. 直接连接就行

    connect()

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    //直接连接就行
    if (connect(client_socket, (struct sockaddr*)&target, sizeof(struct sockaddr)) == -1) {
    	printf("connect server failed!Error Code:%ld\n",GetLastError());
    }

  6. 进行通信

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    while (1) {
    	char buff[BUFSIZ * 4] = { 0 };
    	printf("please input send content:");
    	scanf("%s",buff);
    	int ret = send(client_socket, buff, strlen(buff), 0);
    	if (ret <= 0)
    		break;
    }

最后同时运行两个项目就可以了！

完整源码

服务端

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#include <stdio.h>
#include <WinSock2.h>
#pragma comment(lib,"ws2_32.lib")

int main() {
	WSADATA wsaData;
	WSAStartup(MAKEWORD(2, 2), &wsaData);
	//创建socket
	SOCKET server_socket = socket(AF_INET, SOCK_STREAM, 0);//如果创建失败为-1
	if (server_socket == -1) {
		printf("server socket create failed!Error Code:%d\n", GetLastError());
		exit(-1);
	}
    
	//ip地址 + 端口号
	struct sockaddr_in local;
	local.sin_family = AF_INET;
	local.sin_port = htons(8080);//将8080转换为大端序
	local.sin_addr.S_un.S_addr = inet_addr("0.0.0.0");

	// 绑定socket和端口
	if (bind(server_socket, (struct sockaddr*)&local, sizeof(struct sockaddr_in))
		== -1) {
		printf("bind server socket failed!Error Code:%ld\n", GetLastError());
		exit(-1);
	}

	//监听这个端口
	if (listen(server_socket, 10) == -1) {
		printf("listen server socket failed!Error Code:%ld\n", GetLastError());
		exit(-1);
	}
	printf("bind and listen success. wait client connect ...\n");

	//等待客户端连接 accept函数在进行的过程中就是三次握手
	SOCKET client_socket = accept(server_socket, NULL, NULL);

	while (1) {
		char buff[BUFSIZ * 4] = { 0 };
		int ret = recv(client_socket, buff, BUFSIZ * 4, 0);
		if (ret <= 0) break;
		printf("ret:%d buff:%s\n", ret, buff);

		if (memcmp(buff, "music", strlen("music")) == 0) {
			printf("playing music\r\n");
		}
	}	
	return 0;
}

客户端

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#include <stdio.h>
#include <WinSock2.h>
#pragma comment(lib,"ws2_32.lib")

int main() {
	//开启网络权限
	WSADATA wsaData;
	WSAStartup(MAKEWORD(2, 2), &wsaData);

	//创建socket
	SOCKET client_socket = socket(AF_INET, SOCK_STREAM, 0);
	if (client_socket == -1) {
		printf("client socket create failed!Error Code:%d\n", GetLastError());
		exit(-1);
	}

	//创建目标IP和端口
	struct sockaddr_in target;
	target.sin_family = AF_INET;
	target.sin_port = htons(8080);
	//127.0.0.1本地环回
	//或者填本机ip
	target.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");

	//直接连接就行
	if (connect(client_socket, (struct sockaddr*)&target, sizeof(struct sockaddr)) == -1) {
		printf("connect server failed!Error Code:%ld\n",GetLastError());
	}

	//发消息
	while (1) {
		char buff[BUFSIZ * 4] = { 0 };
		printf("please input send content:");
		scanf("%s",buff);
		int ret = send(client_socket, buff, strlen(buff), 0);
		if (ret <= 0)
			break;
	}

	return 0;
}