Introduction Socket is an interface between an application process and transport layer. The application process can send or receive messages to/from another application process (local or Network) through a socket. Winsock is the lowest level Windows API for TCP/IP programming. Part of the code is located in winsock.dll and the rest is inside the Windows kernel. In this article I shall try to explain how we can create a server and a client using winsock. Background Before going to the main topic I am trying to explain where the socket exists in different network layer. Code: [B] Server [/B] [B] Client[/B] ---------------------- ---------------------- | Application layer | | Application layer | [B]User Space[/B] | | [B]User Space[/B] | | +--------------------+ +--------------------+ | Socket | | Socket | | | | | +--------------------+ +--------------------+ | Transport layer | | Transport layer | | | | | | | | | | | | | | | | | [B]Kernel Space[/B] | Network layer | [B]Kernel Space[/B] | Network layer | | | | | | | | | | | | | | | | | | Link layer | | Link layer | | | | | | | | | | | | | | | | | | Physical layer | | Physical layer | ---------------------- ---------------------- Now I am trying to explain the protocol of client and server and the function needs to call for making this client server connection. Code: [B] Server [/B] [B]Client[/B] ----------------- ----------------- | WSAStartup() | | WSAStartup() | +---------------+ +---------------+ | | | | +---------------+ +---------------+ | socket() | | socket() | +---------------+ +---------------+ | | | | +---------------+ | | | bind() | | | +---------------+ | | | | | | +---------------+ +---------------+ | listen() | <----------- | connect() | +---------------+ +---------------+ | | | | +---------------+ | | | accept() | | | +---------------+ | | | | | | +---------------+ +---------------+ | send() | -----------> | recv() | | | | | | recv() | <----------- | send() | +---------------+ +---------------+ | | | | +---------------+ +---------------+ | closesocket() | | closesocket() | +---------------+ +---------------+ | | | | +---------------+ +---------------+ | WSACleanup() | | WSACleanup() | ----------------- ----------------- The WSAStartup() function initializes the Winsock.dll. The socket() function creates a socket. The bind() function bind a previously created socket to a specified socket address. listen() begin listening on the port specified by the previous bind() call. Server program call accept() immediately after calling Listen(). accept() returns when a client connects to the socket, sending back a new socket that corresponds to the new connection. The client program calls connect() after creating socket. Connect returns when the connection has been made. The send() and recv() are for sending/receiving data to/from socket. The closesocket() function closes an existing socket. WSACleanup() terminates to use of socket dll. The following code will create a server which will communicate with clients. The code Code: #include <stdio.h> #include <windows.h> #include <winsock.h> #define SOCKET_OK 0 int WINAPI WinMain(HINSTANCE hInst, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShow) { WORD sockVer; WSADATA wsaData; int retVal; sockVer = MAKEWORD(2,2); WSAStartup(sockVer, &wsaData); /// Creating socket SOCKET servSock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP); if(servSock == INVALID_SOCKET) { MessageBox(NULL, "Unable to create socket()", "SOCKET ERROR", MB_OK); WSACleanup(); return SOCKET_ERROR; } /// Filling in sockaddr_in struct SOCKADDR_IN sin; sin.sin_family = PF_INET; sin.sin_port = htons(1111); sin.sin_addr.s_addr = INADDR_ANY; retVal = bind(servSock, (LPSOCKADDR)&sin, sizeof(sin)); if(retVal == SOCKET_ERROR) { MessageBox(NULL, "Unable to bind", "SOCKET ERROR", MB_OK); WSACleanup(); return SOCKET_ERROR; } /// Trying to listen socket retVal = listen(servSock, 10); if(retVal == SOCKET_ERROR) { MessageBox(NULL, "Unable to listen()", "SOCKET ERROR", MB_OK); WSACleanup(); return SOCKET_ERROR; } /// Waiting for a client SOCKET clientSock; clientSock = accept(servSock, NULL, NULL); if(clientSock == INVALID_SOCKET) { MessageBox(NULL, "Unable to accept()", "SOCKET ERROR", MB_OK); WSACleanup(); return SOCKET_ERROR; } char szReq[8]; retVal = recv(clientSock, szReq, 8, 0); if(retVal == SOCKET_ERROR) { MessageBox(NULL, "Unable to recv()", "SOCKET ERROR", MB_OK); return SOCKET_ERROR; } MessageBox(NULL, szReq, "Got the request from client", MB_OK); char *szResp = "Response"; MessageBox(NULL, szResp, "Sending response from server", MB_OK); retVal = send(clientSock, szResp, strlen(szResp), 0); if(retVal == SOCKET_ERROR) { MessageBox(NULL, "Unable to send()", "SOCKET ERROR", MB_OK); return SOCKET_ERROR; } /// Closing socket closesocket(clientSock); closesocket(servSock); WSACleanup(); return SOCKET_OK; } Making a client application which will send/ receive data from the server. Code: #include <windows.h> #include <winsock.h> int WINAPI WinMain(HINSTANCE hHinst, HINSTANCE hPrevHinst, LPSTR lpCmdLine, int nShow) { WORD ver = MAKEWORD(2,2); WSADATA wsaData; int retVal=0; WSAStartup(ver,(LPWSADATA)&wsaData); LPHOSTENT hostEnt; /// Collect information of the server hostEnt = gethostbyname("Myxp"); if(!hostEnt) { MessageBox(NULL, "Unable to collect gethostbyname()", "ERROR", MB_OK); WSACleanup(); return 1; } /// Creating a socket SOCKET clientSock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP); if(clientSock == SOCKET_ERROR) { MessageBox(NULL, "Unable to create socket", "ERROR", MB_OK); WSACleanup(); return 1; } SOCKADDR_IN serverInfo; serverInfo.sin_family = PF_INET; serverInfo.sin_addr = *((LPIN_ADDR)*hostEnt->h_addr_list); serverInfo.sin_port = htons(1111); retVal=connect(clientSock,(LPSOCKADDR)&serverInfo, sizeof(serverInfo)); if(retVal==SOCKET_ERROR) { MessageBox(NULL, "Unable to connect()", "ERROR", MB_OK); WSACleanup(); return 1; } MessageBox(NULL, "Connection made sucessfully", "SUCCESS", MB_OK); char *pBuf = "Request"; MessageBox(NULL, "Sending request from client", "SENDING....", MB_OK); retVal = send(clientSock, pBuf, strlen(pBuf), 0); if(retVal == SOCKET_ERROR) { MessageBox(NULL, "Unable to send()", "ERROR", MB_OK); WSACleanup(); return 1; } char szResponse[9]; retVal = recv(clientSock, szResponse, 9, 0); if(retVal == SOCKET_ERROR) { MessageBox(NULL, "Unable to recv()", "SOCKET ERROR", MB_OK); WSACleanup(); return 1; } MessageBox(NULL, szResponse, "Got the response from server", MB_OK); closesocket(clientSock); WSACleanup(); return 0; }
Guys which programming language can i use to write a software. its about a program that will echo or say the name of a person when it sees the person picture. jst for 8 secs it will say the persons name. reply me on hw to go about it. thank you
