学习：WinSock TCP 短连接

TCP Socket编程概念：

服务端程序：创建socket -> bind -> listen -> accept -> recv/send -> close

客户端程序：创建socket -> connect -> recv/send -> close

流式套接字：
1、TCP/IP
2、SOCK_STREAM

网络程序 = 客户端 + 服务端

套接字 socket = IP + PORT

IP地址的转换

inet_ntoa ： 功能是将网络地址转换成"."点隔的字符串格式
inet_aton ： 将字符串形式的IP地址 转换 为一个32位的网络序列IP地址
inet_addr ： 将字符串形式的IP地址 转换 为一个网络字节顺序的整型值

字节转换

ntohl()    // 网络字节顺序转换为主机字节顺序 long 类型
ntohs()    // 网络字节顺序转换为主机字节顺序 short 类型
htonl()    // 主机字节顺序转换为网络字节顺序 long 类型
htons()    // 主机字节顺序转换为网络字节顺序 short类型

注意：如果主机字节顺序是大端，那么转换为网络字节顺序的时候，那么转换后，仍然是大端的字节顺序。

C/S通信示例图如下：

---

实现代码：

服务端：

#include<winSock2.h>
#include<iostream>
#pragma comment(lib, "ws2_32.lib") //添加动态链接库

using namespace std;

int main(int argc, char * argv[]) {
	const int	BUFSIZE = 1024;
	SOCKET		ListeningSocket; //定义一个套接字变量
	SOCKET		NewConnection; //客户端的请求生成的新的套接字
	SOCKADDR_IN ClientAddr;
	SOCKADDR_IN ServerAddr;
	char		Message[BUFSIZE];
	int			ClientAddrLen;
	ZeroMemory(Message, BUFSIZE);
	
	if (argc <= 1)
	{
		cout << "USAGE: TcpServer <Listen Port>" << endl;
		return -1;
	}

	
	int ret; //用来检查初始化成功是否
	WSADATA wsaDATA; // 创建一个WSADATA 用来初始化套接字网络库
	
	if ( (ret = WSAStartup(MAKEWORD(2,2), &wsaDATA)) != 0) { // 初始化套接字网络库WinSock2.2版本
		cout << "WSAStartup初始化失败 with error " << ret << endl;
		return -1;
	}

	//创建套接字 AF_INET协议 SOCK_STREAM流 TCP协议
	if ((ListeningSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == SOCKET_ERROR) {
		cout << "创建套接字失败 with error " << WSAGetLastError() << endl;
		WSACleanup();
		return -1; 
	}

	//绑定套接字
	ServerAddr.sin_family = AF_INET;
	ServerAddr.sin_port = htons(atoi(argv[1]));
	ServerAddr.sin_addr.S_un.S_addr = htonl(INADDR_ANY);

	if (bind(ListeningSocket, (SOCKADDR *)&ServerAddr, sizeof(SOCKADDR)) == SOCKET_ERROR) {
		cout << "绑定套接字失败 with error " << WSAGetLastError() << endl;
		closesocket(ListeningSocket);
		WSACleanup();
		return -1;
	}
	 
	//监听套接字
	if((ret = listen(ListeningSocket, 1)) == SOCKET_ERROR) {
		cout << "监听套接字失败 with error " << WSAGetLastError() << endl;
		closesocket(ListeningSocket);
		WSACleanup();
		return -1;
	}
	cout << "正在监听端口"<< argv[1] << "中..." << endl;


	//接收客户端数据

	ClientAddrLen = sizeof(SOCKADDR);

	if((NewConnection = accept(ListeningSocket,(SOCKADDR*)&ClientAddr, &ClientAddrLen)) == INVALID_SOCKET){//创建一个当前客户端和服务端的套接字
		cout << "创建NewConnection失败 with error " << WSAGetLastError() << endl;
		closesocket(ListeningSocket);
		WSACleanup();
		return -1;
	}

	//关闭套接字
	closesocket(ListeningSocket);

	recv(NewConnection, Message, sizeof(Message), 0);
	cout << "接收到的数据为:" << Message << endl;


	closesocket(NewConnection);
	WSACleanup();
	

	return 0;
}

客户端：

#include<WinSock2.h>
#include<iostream>
#pragma comment(lib, "ws2_32.lib") //添加动态链接库
#pragma warning(disable:4996) //忽略旧函数使用缺陷的警告

using namespace std;

int main(int argc, char * argv[]) {
	const int	BUFSIZE = 1024;
	SOCKET		ClientSocket;
	SOCKADDR_IN ServerAddr;
	char		SendBuf[BUFSIZE];  //发送存储的数据缓冲区
	char		BufRecv[BUFSIZE]; //接收收到的数据缓冲区
	
	ZeroMemory(SendBuf, BUFSIZE);
	ZeroMemory(BufRecv, BUFSIZE);
	strcpy(SendBuf, "Hello, My Name is Client");

	if (argc <= 2)
	{
		cout << "USAGE: TcpServer <Server IP> <Server PORT>" << endl;
		return -1;
	}

	WSADATA		WSAData;
	int			ret;
	if ((ret = WSAStartup(MAKEWORD(2, 2), &WSAData)) != 0) {
		cout << "WSAStartup初始化失败 with error " << ret << endl;
		return -1;
	}
	

	//创建套接字
	if ((ClientSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == SOCKET_ERROR) {
		cout << "创建套接字失败 with error " << WSAGetLastError() << endl;
		WSACleanup();
		return -1;
	}

	//连接connet服务端
	ServerAddr.sin_family = AF_INET;
	ServerAddr.sin_addr.s_addr = inet_addr(argv[1]);
	ServerAddr.sin_port = htons(atoi(argv[2]));
	if (connect(ClientSocket, (SOCKADDR *)&ServerAddr, sizeof(ServerAddr)) == SOCKET_ERROR) {
		cout << "连接服务端失败 with error " << WSAGetLastError() << endl;
		closesocket(ClientSocket);
		WSACleanup();
		return -1;
	}

	cout << "连接建立成功!";


	//send发送数据
	if ((ret = send(ClientSocket, SendBuf, strlen(SendBuf), 0)) == SOCKET_ERROR){
		cout << "send failed with error " << WSAGetLastError() << endl;;
		closesocket(ClientSocket);
		WSACleanup();
		return -1;
	}

	//关闭套接字
	closesocket(ClientSocket);
	WSACleanup();
	return 0;
}

结果图：