Winsock网络编程

1.网络编程的基本步骤

在网络编程中，一般分Server和Client端两种。
其中Server端的步骤基本如下：
1． 初始化Winsock
2． 创建socket
3． 绑定 socket
4． 在socket上监听客户端
5． 接受来自client的连接
6． 接受和发送数据
7． 断开连接

Client端的步骤基本如下:
1. 初始化Winsock
2. 创建socket
3. 连接到Server
4. 发送和接受数据
5. 断开连接

2.Winsock加载和卸载

要使用Windows Socket API进行编程，一般在程序开始要用WSAStartup进行初始化动态库，在程序结束要用WSACleanup进行卸载Winsock动态库。
包括的头文件是：

#include 

要加载的库是：

#pragma comment(lib,"Ws2_32.lib")

WSAStartup函数：初始化Winsock动态库

int WSAStartup(
  _In_  WORD      wVersionRequested,
  _Out_ LPWSADATA lpWSAData
);

其中wVersionRequested是指调用者能使用的Windows Sockets指定的最高版本号；
lpWSAData是要接收Windows套接字实现的详细信息的WSAData数据结构体指针。
返回值：
如果成功，返回0，否则返回错误码。

3.代码实现

3.1 Server端代码

// ServerCmd.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include 
#include 

#pragma comment(lib,"Ws2_32.lib")

int main()
{
    WSADATA wsaData;
    SOCKET serverSocket;

    int nResult = 0;

    //初始化动态库
    nResult = WSAStartup(MAKEWORD(2, 2), &wsaData);

    //创建WSASocket
    serverSocket = WSASocket(AF_INET, SOCK_STREAM, 0, NULL, 0, WSA_FLAG_OVERLAPPED);

    IN_ADDR addr;
    InetPton(AF_INET, L"192.168.165.100", (void*)&addr);

    SOCKADDR_IN addrIn;
    addrIn.sin_family = AF_INET;
    addrIn.sin_addr.S_un.S_addr = addr.S_un.S_addr;
    addrIn.sin_port = htons(4303);

    //绑定socket
    //The bind function associates a local address with a socket.
    nResult = bind(serverSocket, (SOCKADDR*)&addrIn, sizeof(SOCKADDR_IN));
    if (nResult == SOCKET_ERROR) {
        printf("errorCode = %d\n", WSAGetLastError());
        closesocket(serverSocket);
        WSACleanup();
        return 1;
    }
    else {
        printf("bind success!\n");
    }

    //监听
    //The listen function places a socket in a state in which it is listening for an incoming connection.
    //If no error occurs, listen returns zero. Otherwise, a value of SOCKET_ERROR is returned, and a specific error code can be retrieved by calling WSAGetLastError.
    nResult = listen(serverSocket, 100);
    if (nResult != 0) {
        printf("errorCode = %d\n", WSAGetLastError());
        closesocket(serverSocket);
        WSACleanup();
        return 1;
    }
    else {
        printf("listen success!\n");
    }   

    SOCKET clientSocket;
    char recvBuf[100];
    memset(recvBuf, 0, 100 * sizeof(char));

    printf("Start Server:\n");
    //接收客户端的连接
    //The accept function permits an incoming connection attempt on a socket.
    clientSocket = accept(serverSocket, NULL, NULL);
    if (clientSocket == INVALID_SOCKET) {
        printf("errorCode = %d\n", WSAGetLastError());
        closesocket(serverSocket);
        WSACleanup();
        return 1;
    }
    else {
        printf("accept success.\n");
    }

    while (1) {
        //接收客户端发送的消息
        nResult = recv(clientSocket, recvBuf, 100, 0);
        if (nResult > 0) {
            printf("recv msg : %s \n", recvBuf);
        }   
    }

    //关闭socket
    closesocket(serverSocket);

    WSACleanup();

    system("pause");

    return 0;
}

3.2 Client端代码

// ClientCmd.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include 
#include 

#pragma comment(lib,"Ws2_32.lib")

int main()
{
    WSADATA wsaData = { 0 };
    int nResult = 0;
    char sendBuf[] = "This is a test message.";

    SOCKET socket;

    socket = INVALID_SOCKET;

    //If successful, the WSAStartup function returns zero. 
    //Otherwise, it returns one of the error codes listed below.
    nResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
    if (nResult != 0) {
        printf("errorCode = %d\n",WSAGetLastError());
        WSACleanup();
        return 1;
    }

    //创建WSASocket
    socket = WSASocket(AF_INET, SOCK_STREAM, 0, NULL, 0, WSA_FLAG_OVERLAPPED);
    if (socket == INVALID_SOCKET) {
        printf("errorCode = %d\n", WSAGetLastError());
        WSACleanup();
        return 1;
    }

    //SOCKADDR_IN addr;
    //addr.sin_family = AF_INET;
    //addr.sin_addr.S_un.S_addr = inet_addr("192.168.165.100");
    //addr.sin_port = htons(4303);

    IN_ADDR addr;
    InetPton(AF_INET, L"192.168.165.100", (void*)&addr);

    SOCKADDR_IN addrIn;
    addrIn.sin_family = AF_INET;
    addrIn.sin_addr.S_un.S_addr = addr.S_un.S_addr;
    addrIn.sin_port = htons(4303);

    //连接服务器
    //If no error occurs, connect returns zero. 
    //Otherwise, it returns SOCKET_ERROR, 
    //and a specific error code can be retrieved by calling WSAGetLastError.
    //connect(socket, (const SOCKADDR*)&address, sizeof(SOCKADDR));
    nResult = connect(socket, (SOCKADDR*)&addrIn, sizeof(SOCKADDR_IN));

    if (nResult == SOCKET_ERROR) {
        printf("errorCode = %d\n", WSAGetLastError());
        closesocket(socket);
        WSACleanup();
        return 1;
    }

    //发送数据
    nResult = send(socket, sendBuf, (int)strlen(sendBuf), SOCK_STREAM);
    if (nResult == SOCKET_ERROR) {
        printf("errorCode = %d\n", WSAGetLastError());
        closesocket(socket);
        WSACleanup();
        return 1;
    }

    //关闭socket
    closesocket(socket);

    WSACleanup();

    system("pause");

    return 0;
}

3.3 服务器端运行结果

bind success!
listen success!
Start Server:
accept success.
recv msg : This is a test message