一个服务器，接受客户连接，返回客户IP地址，并关闭连接。


一个服务器程序的基本步骤：

1. winsock library 的初始化

2. 创建socket

3. 服务器地址

4. bind->listen

5. 等待客户连接 accept

6. 处理客户接入

7. 关闭 socket

8. 释放资源：winsock library




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

//


#include 
"stdafx.h"

#include 
<winsock2.h>

#pragma comment(lib,
"ws2_32"
)

#include 
"SimpleTcpServer.h"


#include 
<conio.h>


#ifdef _DEBUG

#define 
new

 DEBUG_NEW

#undef THIS_FILE

static

 char

 THIS_FILE[] = __FILE__
;
#endif


/

// The one and only application object

//z 2011-05-22 21:23:03@is2120




CWinApp theApp;

using

 namespace

 std;



UINT  ServerThread(LPVOID pParam);

int

 _tmain(int

 argc, TCHAR* argv[], TCHAR* envp[])


{


  int

 nRetCode = 0
;



  // initialize MFC and print and error on failure



  if
 (!AfxWinInit(::GetModuleHandle(NULL
), NULL
, ::GetCommandLine(), 0
))


  {


    // 
TODO

: change error code to suit your needs



    cerr << _T("Fatal Error: MFC initialization failed"
) << endl;


    nRetCode = 1
;


  }


  else



  {


    // 
TODO

: code your application's behavior here.



    /*

    CString strHello;

    strHello.LoadString(IDS_HELLO);

    cout << (LPCTSTR)strHello << endl;

    
*/



    int

 nRetCode = 0
; 


    


    cout << "Press ESCAPE to terminate program
/r/n
"
;


    AfxBeginThread(ServerThread,0
);


    while
(_getch()!=27
);


    


    return

 nRetCode;


  }



  return

 nRetCode;


}



UINT  ServerThread(LPVOID pParam)


{ 


    cout << "Starting up TCP server
/r/n
"
;



    //A SOCKET is simply a typedef for an unsigned int.




    //In Unix, socket handles were just about same as file 




    //handles which were again unsigned ints.




    //Since this cannot be entirely true under Windows




    //a new data type called SOCKET was defined.




    SOCKET server;



    //WSADATA is a struct that is filled up by the call 




    //to WSAStartup




    WSADATA wsaData;



    //The sockaddr_in specifies the address of the socket




    //for TCP/IP sockets. Other protocols use similar structures.




    sockaddr_in local;



    //WSAStartup initializes the program for calling WinSock.




    //The first parameter specifies the highest version of the 




    //WinSock specification, the program is allowed to use.




    int

 wsaret=WSAStartup(0x101
,&wsaData);



    //WSAStartup returns zero on success.




    //If it fails we exit.




    if
(wsaret!=0
)


    {


        return

 0
;


    }



    //Now we populate the sockaddr_in structure




    local.sin_family=AF_INET; //Address family




    local.sin_addr.s_addr=INADDR_ANY; //Wild card IP address




    local.sin_port=htons((u_short)20248
); //port to use




    //the socket function creates our SOCKET




    server=socket(AF_INET,SOCK_STREAM,0
);



    //If the socket() function fails we exit




    if
(server==INVALID_SOCKET)


    {


        return

 0
;


    }



    //bind links the socket we just created with the sockaddr_in 




    //structure. Basically it connects the socket with 




    //the local address and a specified port.




    //If it returns non-zero quit, as this indicates error




    if
(bind(server,(sockaddr*)&local,sizeof
(local))!=0
)


    {


        return

 0
;


    }



    //listen instructs the socket to listen for incoming 




    //connections from clients. The second arg is the backlog




    if
(listen(server,10
)!=0
)


    {


        return

 0
;


    }



    //we will need variables to hold the client socket.




    //thus we declare them here.




    SOCKET client;


    sockaddr_in from;


    int

 fromlen=sizeof
(from);



    while
(true
)//we are looping endlessly




    {


        char

 temp[512
];



        //accept() will accept an incoming




        //client connection




        client=accept(server,


            (struct

 sockaddr*)&from,&fromlen);


    


        sprintf(temp,"Your IP is 
%s
/r/n
"
,inet_ntoa(from.sin_addr));



        //we simply send this string to the client




        send(client,temp,strlen(temp),0
);


        cout << "Connection from "
 << inet_ntoa(from.sin_addr) <<"
/r/n
"
;


    


        //close the client socket




        closesocket(client);



    }



    //closesocket() closes the socket and releases the socket descriptor




    closesocket(server);



    //originally this function probably had some use




    //currently this is just for backward compatibility




    //but it is safer to call it as I still believe some




    //implementations use this to terminate use of WS2_32.DLL 




    WSACleanup();



    return

 0
;


}