Network programming-TCP model

Server

1. Initialize WSA.


2. Create a socket.


3. Bind the socket.


4. Listen on the socket.


5. Accept a connection.


6. Send and receive data.


7. Disconnect.

Client

1. Initialize WSA.


2. Create a socket.


3. Connect to the server.


4. Send and receive data.


5. Disconnect.

Server Source Code

#include <stdio.h>
#include "winsock2.h"

void main() {

    // Initialize Winsock.
    WSADATA wsaData;
    int iResult = WSAStartup( MAKEWORD(2,2), &wsaData );
    if ( iResult != NO_ERROR )
        printf("Error at WSAStartup()\n");

    // Create a socket.
    SOCKET m_socket;
    m_socket = socket( AF_INET, SOCK_STREAM, IPPROTO_TCP );

    if ( m_socket == INVALID_SOCKET ) {
        printf( "Error at socket(): %ld\n", WSAGetLastError() );
        WSACleanup();
        return;
    }

    // Bind the socket.
    sockaddr_in service;

    service.sin_family = AF_INET;
    service.sin_addr.s_addr = inet_addr( "127.0.0.1" );
    service.sin_port = htons( 27015 );

    if ( bind( m_socket, (SOCKADDR*) &service, sizeof(service) ) == SOCKET_ERROR ) {
        printf( "bind() failed.\n" );
        closesocket(m_socket);
        return;
    }
    
    // Listen on the socket.
    if ( listen( m_socket, 1 ) == SOCKET_ERROR )
        printf( "Error listening on socket.\n");

    // Accept connections.
    SOCKET AcceptSocket;

    printf( "Waiting for a client to connect...\n" );
    while (1) {
        AcceptSocket = SOCKET_ERROR;
        while ( AcceptSocket == SOCKET_ERROR ) {
            AcceptSocket = accept( m_socket, NULL, NULL );
        }
        printf( "Client Connected.\n");
        m_socket = AcceptSocket; 
        break;
    }
    
    // Send and receive data.
    int bytesSent;
    int bytesRecv = SOCKET_ERROR;
    char sendbuf[32] = "Server: Sending Data.";
    char recvbuf[32] = "";
    
    bytesRecv = recv( m_socket, recvbuf, 32, 0 );
    printf( "Bytes Recv: %ld\n", bytesRecv );
    
    bytesSent = send( m_socket, sendbuf, strlen(sendbuf), 0 );
    printf( "Bytes Sent: %ld\n", bytesSent );

    return;
}

Client Source Code

#include <stdio.h>
#include "winsock2.h"

void main() {

    // Initialize Winsock.
    WSADATA wsaData;
    int iResult = WSAStartup( MAKEWORD(2,2), &wsaData );
    if ( iResult != NO_ERROR )
        printf("Error at WSAStartup()\n");

    // Create a socket.
    SOCKET m_socket;
    m_socket = socket( AF_INET, SOCK_STREAM, IPPROTO_TCP );

    if ( m_socket == INVALID_SOCKET ) {
        printf( "Error at socket(): %ld\n", WSAGetLastError() );
        WSACleanup();
        return;
    }

    // Connect to a server.
    sockaddr_in clientService;

    clientService.sin_family = AF_INET;
    clientService.sin_addr.s_addr = inet_addr( "127.0.0.1" );
    clientService.sin_port = htons( 27015 );

    if ( connect( m_socket, (SOCKADDR*) &clientService, sizeof(clientService) ) == SOCKET_ERROR) {
        printf( "Failed to connect.\n" );
        WSACleanup();
        return;
    }

    // Send and receive data.
    int bytesSent;
    int bytesRecv = SOCKET_ERROR;
    char sendbuf[32] = "Client: Sending data.";
    char recvbuf[32] = "";

    bytesSent = send( m_socket, sendbuf, strlen(sendbuf), 0 );
    printf( "Bytes Sent: %ld\n", bytesSent );

    while( bytesRecv == SOCKET_ERROR ) {
        bytesRecv = recv( m_socket, recvbuf, 32, 0 );
        if ( bytesRecv == 0 || bytesRecv == WSAECONNRESET ) {
            printf( "Connection Closed.\n");
            break;
        }
        if (bytesRecv < 0)
            return;
        printf( "Bytes Recv: %ld\n", bytesRecv );
    }

    return;
}