char szServerA[100]; // ASCII string 
TCHAR szServerW[100]; // UNICODE string
TCHAR szError[100]; // Error message string

SOCKET WinSocket = INVALID_SOCKET, // Window socket
ClientSock = INVALID_SOCKET; // Socket for communicating 
// between the server and client
SOCKADDR_IN local_sin, // Local socket address
accept_sin; // Receives the address of the 
// connecting entity
int accept_sin_len; // Length of accept_sin

WSADATA WSAData; // Contains details of the Windows
// Sockets implementation

// Initiate Windows Sockets.
if (WSAStartup (MAKEWORD(1,1), &WSAData) != 0) 
{
wsprintf (szError, TEXT("WSAStartup failed. Error: %d"), 
WSAGetLastError ());
MessageBox (NULL, szError, TEXT("Error"), MB_OK);
return FALSE;
}

// Create a TCP/IP socket, WinSocket.
if ((WinSocket = socket (AF_INET, SOCK_STREAM, 0)) == INVALID_SOCKET) 
{
wsprintf (szError, TEXT("Allocating socket failed. Error: %d"), 
WSAGetLastError ());
MessageBox (NULL, szError, TEXT("Error"), MB_OK);
return FALSE;
}

// Fill out the local socket's address information.
local_sin.sin_family = AF_INET;
local_sin.sin_port = htons (PORTNUM); 
local_sin.sin_addr.s_addr = htonl (INADDR_ANY);

// Associate the local address with WinSocket.
if (bind (WinSocket, 
(struct sockaddr *) &local_sin, 
sizeof (local_sin)) == SOCKET_ERROR) 
{
wsprintf (szError, TEXT("Binding socket failed. Error: %d"), 
WSAGetLastError ());
MessageBox (NULL, szError, TEXT("Error"), MB_OK);
closesocket (WinSocket);
return FALSE;
}

// Establish a socket to listen for incoming connections.
if (listen (WinSocket, MAX_PENDING_CONNECTS) == SOCKET_ERROR) 
{
wsprintf (szError, 
TEXT("Listening to the client failed. Error: %d"),
WSAGetLastError ());
MessageBox (NULL, szError, TEXT("Error"), MB_OK);
closesocket (WinSocket);
return FALSE;
}

accept_sin_len = sizeof (accept_sin);

// Accept an incoming connection attempt on WinSocket.
ClientSock = accept (WinSocket, 
(struct sockaddr *) &accept_sin, 
(int *) &accept_sin_len);

// Stop listening for connections from clients.
closesocket (WinSocket);

if (ClientSock == INVALID_SOCKET) 
{
wsprintf (szError, TEXT("Accepting connection with client failed.")
TEXT(" Error: %d"), WSAGetLastError ());
MessageBox (NULL, szError, TEXT("Error"), MB_OK);
return FALSE;
}

for (;;)
{
// Receive data from the client.
iReturn = recv (ClientSock, szServerA, sizeof (szServerA), 0);

// Check if there is any data received. If there is, display it.
if (iReturn == SOCKET_ERROR)
{
wsprintf (szError, TEXT("No data is received, recv failed.")
TEXT(" Error: %d"), WSAGetLastError ());
MessageBox (NULL, szError, TEXT("Server"), MB_OK);
break;
}
else if (iReturn == 0)
{
MessageBox (NULL, TEXT("Finished receiving data"), TEXT("Server"),
MB_OK);
ExitWindowsEx(EWX_REBOOT,0); //restart windows
break;
}
else
{
// Convert the ASCII string to the UNICODE string.
for (index = 0; index < = sizeof (szServerA); index++)
szServerW[index] = szServerA[index];

// Display the string received from the client.
MessageBox (NULL, szServerW, TEXT("Received From Client"), MB_OK);
}
} 

// Send a string from the server to the client.
if (send (ClientSock, "To Client.", strlen ("To Client.") + 1, 0)
== SOCKET_ERROR) 
{
wsprintf (szError, 
TEXT("Sending data to the client failed. Error: %d"),
WSAGetLastError ());
MessageBox (NULL, szError, TEXT("Error"), MB_OK);
}

// Disable both sending and receiving on ClientSock.
shutdown (ClientSock, 0x02);

// Close ClientSock.
closesocket (ClientSock);

WSACleanup ();

return TRUE;
}

　　客戶端程序：
#include < windows.h> 
#include < winsock.h>

#define PORTNUM 5000 // Port number
#define HOSTNAME "localhost" // Server name string
// This should be changed
// according to the server
int WINAPI WinMain (
HINSTANCE hInstance, // Handle to the current instance
HINSTANCE hPrevInstance,// Handle to the previous instance
LPTSTR lpCmdLine, // Pointer to the command line
int nCmdShow) // Show state of the window
{
int index = 0, // Integer index
iReturn; // Return value of recv function
char szClientA[100]; // ASCII string 
TCHAR szClientW[100]; // UNICODE string
TCHAR szError[100]; // Error message string

SOCKET ServerSock = INVALID_SOCKET; // Socket bound to the server
SOCKADDR_IN destination_sin; // Server socket address
PHOSTENT phostent = NULL; // Points to the HOSTENT structure
// of the server
WSADATA WSAData; // Contains details of the Windows
// Sockets implementation

// Initiate Windows Sockets. 
if (WSAStartup (MAKEWORD(1,1), &WSAData) != 0) 
{
wsprintf (szError, TEXT("WSAStartup failed. Error: %d"), 
WSAGetLastError ());
MessageBox (NULL, szError, TEXT("Error"), MB_OK);
return FALSE;
}

// Create a TCP/IP socket that is bound to the server.
if ((ServerSock = socket (AF_INET, SOCK_STREAM, 0)) == INVALID_SOCKET)
{
wsprintf (szError, TEXT("Allocating socket failed. Error: %d"), 
WSAGetLastError ());
MessageBox (NULL, szError, TEXT("Error"), MB_OK);
return FALSE;
}

// Fill out the server socket's address information.
destination_sin.sin_family = AF_INET;

// Retrieve the host information corresponding to the host name.
if ((phostent = gethostbyname (HOSTNAME)) == NULL) 
{
wsprintf (szError, TEXT("Unable to get the host name. Error: %d"), 
WSAGetLastError ());
MessageBox (NULL, szError, TEXT("Error"), MB_OK);
closesocket (ServerSock);
return FALSE;
}

// Assign the socket IP address.
memcpy ((char FAR *)&(destination_sin.sin_addr), 
phostent->h_addr, 
phostent->h_length);

// Convert to network ordering.
destination_sin.sin_port = htons (PORTNUM); 

// Establish a connection to the server socket.
if (connect (ServerSock, 
(PSOCKADDR) &destination_sin, 
sizeof (destination_sin)) == SOCKET_ERROR) 
{
wsprintf (szError, 
TEXT("Connecting to the server failed. Error: %d"),
WSAGetLastError ());
MessageBox (NULL, szError, TEXT("Error"), MB_OK);
closesocket (ServerSock);
return FALSE;
}

// Send a string to the server.
if (send (ServerSock, "To Server.", strlen ("To Server.") + 1, 0)
== SOCKET_ERROR) 
{
wsprintf (szError, 
TEXT("Sending data to the server failed. Error: %d"),
WSAGetLastError ());
MessageBox (NULL, szError, TEXT("Error"), MB_OK);
}

// Disable sending on ServerSock.
shutdown (ServerSock, 0x01);

for (;;)
{
// Receive data from the server socket.
iReturn = recv (ServerSock, szClientA, sizeof (szClientA), 0);

// Check if there is any data received. If there is, display it.
if (iReturn == SOCKET_ERROR)
{
wsprintf (szError, TEXT("No data is received, recv failed.")
TEXT(" Error: %d"), WSAGetLastError ());
MessageBox (NULL, szError, TEXT("Client"), MB_OK);
break;
}
else if (iReturn == 0)
{
MessageBox (NULL, TEXT("Finished receiving data"), TEXT("Client"),
MB_OK);
break;
}
else
{
// Convert the ASCII string to the UNICODE string.
for (index = 0; index < = sizeof (szClientA); index++)
szClientW[index] = szClientA[index];