Talk about C++ Socket programming

There are three types of programming for sockets: streaming socket (SOCK_STREAM), datagram socket (SOCK_DGRAM), original socket (SOCK_RAW). TCP-based socket programming is using streaming sockets.

Steps of server-side programming:

1: load the socket library and create the socket (WSAStartup()/socket());

2: bind the socket to 1 IP address and 1 port (bind());

3: set the socket to listen mode and wait for the connection request (listen());

4: after the request arrives, accept the connection request and return a new socket (accept()) corresponding to the connection;

5: use the returned socket to communicate with the client (send()/recv());

6: return and wait for another connection request;

7: close the socket and close the loaded socket library (closesocket()/WSACleanup()).

Steps of client programming:

1: load the socket library and create the socket (WSAStartup()/socket());

2: make a connection request to the server (connect());

3: communicate with the server (send()/recv());

4: close the socket and close the loaded socket library (closesocket()/WSACleanup()).

Type 1: load/release Winsock library:

1. Loading method:

WSADATA wsa;

/* Initialize the socket resources */

if (WSAStartup(MAKEWORD(1,1),&wsa) != 0)

{

return; // On behalf of the failure 

}

2. Release method:

WSACleanup();

Formula 2: construct SOCKET:

1. Server side: construct listening SOCKET and streaming SOCKET.

SOCKET  Listen_Sock  = socket(AF_INET, SOCK_STREAM, 0)

2. Client: construct communication SOCKET and streaming SOCKET.

SOCKET    Client _Sock   = socket(AF_INET, SOCK_STREAM, 0)

Type 3: configure the listening address and port:

1. Server: SOCKADDR_IN

serverAddr
 ZeroMemory((char *)& serverAddr ,sizeof( serverAddr )); 
serverAddr .sin_family = AF_INET ; 

serverAddr .sin_port = htons( 1234 );     /* Local listening port :1234*/ 

serverAddr .sin_addr.s_addr = htonl( INADDR_ANY ); /* There are IP*/ 

Type 4: bind SOCKET:

1. Server side: binding listens to SOCKET.

bind( Listen_Sock, (struct sockaddr *)& serverAddr, sizeof( serverAddr ))

Type 5: server/client connection:

1. Server: wait for the client to access.

SOCKET  Command_Sock  = accept( Listen_Sock , ...)

2. Client: request connection with the server.

int ret = connect( Client_Sock , ...)

Type 6: receiving/sending data:

1. Server: wait for the client to access.char buf[1024].

Received data :recv(Command_Sock,buf,...)

or

Send data :send(Command_Sock,buf,...)

2. Client: request connection with server.char buf[1024].

Send data :send(Client _Sock,buf,...)

or

Received data :recv(Client _Sock,buf,...)

Type 7: closing SOCKET:

1. Server: close SOCKET.

closesocket( Listen_Sock )

closesocket( Command_Sock )

2. Client: close SOCKET.

closesocket( Client_Sock ) 
 
#include <stdio.h>
#include <Winsock2.h>
void main()
{
 WORD wVersionRequested;
 WSADATA wsaData;
 int err;
 
 wVersionRequested = MAKEWORD( 1, 1 );
 
 err = WSAStartup( wVersionRequested, &wsaData );
 if ( err != 0 ) {
 return;
 }
 
 if ( LOBYTE( wsaData.wVersion ) != 1 ||
    HIBYTE( wsaData.wVersion ) != 1 ) {
 WSACleanup( );
 return;
 }
 SOCKET sockClient=socket(AF_INET,SOCK_STREAM,0);
 
 SOCKADDR_IN addrSrv;
 addrSrv.sin_addr.S_un.S_addr=inet_addr("127.0.0.1");
 addrSrv.sin_family=AF_INET;
 addrSrv.sin_port=htons(6000);
 connect(sockClient,(SOCKADDR*)&addrSrv,sizeof(SOCKADDR));
 send(sockClient,"hello",strlen("hello")+1,0);
 char recvBuf[50];
 recv(sockClient,recvBuf,50,0);
 printf("%s\n",recvBuf);
 
 closesocket(sockClient);
 WSACleanup();
}