MFC的SOCKET的TCP客户端

女爷i 2022-06-04 01:59 317阅读 0赞

前几篇博客介绍了一些TCP/IP、本地修改IP等相关知识，这篇博客进入正题，介绍socket编程的知识。

都是一些入门的知识，老鸟直接飞过就好。

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PC端调试助手有很多：[http://www.cmsoft.cn][http_www.cmsoft.cn]

抓包工具，用wireshark [ http://download.csdn.net/download/wuhenyouyuyouyu/10141313][http_download.csdn.net_download_wuhenyouyuyouyu_10141313]

一些函数使用方法，返回值意义，以及一些参看，请看VS2010的MSDN，或者官方网站：

[https://technet.microsoft.com/zh-cn/library/1s9cycf8][https_technet.microsoft.com_zh-cn_library_1s9cycf8]

MFC使用socket有以下方法：

1、win32的API；

2、CAsyncSocket；

3、CSocket；

这里要介绍的是CSocket。

1、需要的头文件

\#include <WinSock2.h>  
\#include <Ws2tcpip.h>  
\#include <Iphlpapi.h>  
\#include <iostream>  
\#include <Mstcpip.h>  
  
  
\#include <WinError.h>  
  
  
\#include <comdef.h>  
\#include <Wbemidl.h>  
\#include "atlbase.h"  
  
  
\#pragma comment(lib, "wbemuuid.lib")  
  
  
//using namespace std;  
\#pragma comment(lib,"Iphlpapi.lib") //需要添加Iphlpapi.lib库  
\#pragma comment(lib,"dhcpcsvc.lib") //需要添加dhcpcsvc.lib库

2、使用套接字需要先初始化，不初始化直接用，会断言失败

WSADATA wSd\_;  
int message\_code;  
message\_code = WSAStartup(MAKEWORD(2,2),&wSd\_);  
if(0 != message\_code)\{  
OutputDebugString("WSAStartup fail \\n");  
\}  
或者  
AfxSocketInit();

我用的AfxSocketInit();初始化一次即可。

3、创建socket

网上都建议不要用create，用socket创建，

我是用MySocket继承CSocket，然后直接调用

CSocket::Socket();---->>>>CAsyncSocket::Socket();--->>>>socket();

BOOL CAsyncSocket::Socket(int nSocketType, long lEvent,
    	int nProtocolType, int nAddressFormat)
    {
    	ASSERT(m_hSocket == INVALID_SOCKET);
    
    	m_hSocket = socket(nAddressFormat,nSocketType,nProtocolType);
    	if (m_hSocket != INVALID_SOCKET)
    	{
    		CAsyncSocket::AttachHandle(m_hSocket, this, FALSE);
    		return AsyncSelect(lEvent);
    	}
    	return FALSE;
    }

4、关闭socket,我直接调用的CSocket::Close();

CSocket::Close();

void CSocket::Close()
    {
    	if (m_hSocket != INVALID_SOCKET)
    	{
    		CancelBlockingCall();
    
    		VERIFY(AsyncSelect(0));
    		CAsyncSocket::Close();
    		m_hSocket = INVALID_SOCKET;
    	}
    }

void CAsyncSocket::Close()
    {
    	if (m_hSocket != INVALID_SOCKET)
    	{
    		VERIFY(SOCKET_ERROR != closesocket(m_hSocket));
    		CAsyncSocket::KillSocket(m_hSocket, this);
    		m_hSocket = INVALID_SOCKET;
    	}
    }

void PASCAL CAsyncSocket::KillSocket(SOCKET hSocket, CAsyncSocket* pSocket)
    {
    	ASSERT(CAsyncSocket::LookupHandle(hSocket, FALSE) != NULL);
    
    	_AFX_SOCK_THREAD_STATE* pState = _afxSockThreadState;
    
    	CAsyncSocket::DetachHandle(hSocket, FALSE);
    	if (pState->m_hSocketWindow != NULL)
    	{
    		::PostMessage(pState->m_hSocketWindow, WM_SOCKET_DEAD,
    			(WPARAM)hSocket, 0L);
    		CAsyncSocket::AttachHandle(hSocket, pSocket, TRUE);
    	}
    }

通过以上过程，我们知道，CSocket::Socket()和CSocket::Close()必须成对调用。

（这些函数在socketcore.cpp里面）

5、CSocket的消息

所有的回调函数都是以这个函数为基础，然后根据不同的消息类型，回调不同的消息

void PASCAL CAsyncSocket::DoCallBack(WPARAM wParam, LPARAM lParam)
    {
    	if (wParam == 0 && lParam == 0)
    		return;
    
    	// Has the socket be closed - lookup in dead handle list
    	CAsyncSocket* pSocket = CAsyncSocket::LookupHandle((SOCKET)wParam, TRUE);
    
    	// If yes ignore message
    	if (pSocket != NULL)
    		return;
    
    	pSocket = CAsyncSocket::LookupHandle((SOCKET)wParam, FALSE);
    	if (pSocket == NULL)
    	{
    		// Must be in the middle of an Accept call
    		pSocket = CAsyncSocket::LookupHandle(INVALID_SOCKET, FALSE);
    		ASSERT(pSocket != NULL);
    
    		if(pSocket == NULL)
    			return;
    			
    		pSocket->m_hSocket = (SOCKET)wParam;
    		CAsyncSocket::DetachHandle(INVALID_SOCKET, FALSE);
    		CAsyncSocket::AttachHandle(pSocket->m_hSocket, pSocket, FALSE);
    	}
    
    	int nErrorCode = WSAGETSELECTERROR(lParam);
    	switch (WSAGETSELECTEVENT(lParam))
    	{
    	case FD_READ:
    		{
    			fd_set fds;
    			int nReady;
    			timeval timeout;
    
    			timeout.tv_sec = 0;
    			timeout.tv_usec = 0;
    
    			FD_ZERO(&fds);
    			FD_SET(pSocket->m_hSocket, &fds);
    			nReady = select(0, &fds, NULL, NULL, &timeout);
    			if (nReady == SOCKET_ERROR)
    				nErrorCode = WSAGetLastError();
    			if ((nReady == 1) || (nErrorCode != 0))
    				pSocket->OnReceive(nErrorCode);
    		}
    		break;
    	case FD_WRITE:
    		pSocket->OnSend(nErrorCode);
    		break;
    	case FD_OOB:
    		pSocket->OnOutOfBandData(nErrorCode);
    		break;
    	case FD_ACCEPT:
    		pSocket->OnAccept(nErrorCode);
    		break;
    	case FD_CONNECT:
    		pSocket->OnConnect(nErrorCode);
    		break;
    	case FD_CLOSE:
    		pSocket->OnClose(nErrorCode);
    		break;
    	}
    }

当服务器正常关闭，调用closesocket()时候，客户端就是触发OnClose，如果是客户端自己主动断开，则不会触发这个消息。

6、当服务器异常重启或者掉电，网线被拔掉，怎么检测呢？

这个时候需要开启socket的keepalive功能，如果服务器异常断开，就会超时触发OnClose消息

需要包含头文件\#include <Mstcpip.h>

bool CMySocket::mySetKeepAlive(void)
    {
        //开启KeepAlive
        DWORD nValue = 1;
        int nRet=0;
        nRet = CSocket::SetSockOpt(SO_KEEPALIVE,&nValue,sizeof(nValue));
        if(!nRet){
            UserOutputDebugString_LastError();
            return false;
        }
    
        struct tcp_keepalive alive_in = {0};
        struct tcp_keepalive alive_out= {0};
        alive_in.keepalivetime        = 5000;   //开始首次KeepAlive探测前的TCP关闭时间
        alive_in.keepaliveinterval    = 1000;   //两次KeepAlive探测的时间间隔
        alive_in.onoff                = TRUE;
        unsigned long nlBytesReturn   = 0;
    
        nRet = WSAIoctl(this->m_hSocket,
                        SIO_KEEPALIVE_VALS,
                        &alive_in,
                        sizeof(alive_in),
                        &alive_out,
                        sizeof(alive_out),
                        &nlBytesReturn,
                        NULL,
                        NULL);
    
        if(SOCKET_ERROR == nRet){
            UserOutputDebugString_LastError();
            return false;
        }
        return true;
    }

我感觉这个东西，类似心跳包。

![20171201201748775][]

7、connect时候快速返回结果

设置非阻塞模式
        unsigned long flag = 1;       //1：为非阻塞模式；0：为阻塞模式
        CSocket::IOCtl(FIONBIO,&flag);//FIONBIO 允许或者禁止套接字s的非阻塞模式

[http_www.usr.cn_Download_29.html]: http://www.usr.cn/Download/29.html
[http_www.cmsoft.cn]: http://www.cmsoft.cn
[http_download.csdn.net_download_wuhenyouyuyouyu_10141313]: http://download.csdn.net/download/wuhenyouyuyouyu/10141313
[https_technet.microsoft.com_zh-cn_library_1s9cycf8]: https://technet.microsoft.com/zh-cn/library/1s9cycf8
[20171201201748775]: /images/20220604/18701254e997491eb7d745b6ece163a8.png