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Winsock 2 I/O Methods 5 Part 2

 

 

What do we have in this chapter 5 part 2?

  1. The select() Program Example

  2. The Client Test Program Example

 

The select() Program Example

 

The following program example demonstrates the use of select() for server/receiver program.

 

Winsock 2 socket I/O Methods: A program example demonstrates the use of select() for server/receiver program - Create a new empty Win32 console mode application and add the project/solution name.

 

Add the following source code.

 

// Description:

//

//    This sample illustrates how to develop a simple echo server Winsock

//    application using the select() API I/O model. This sample is

//    implemented as a console-style application and simply prints

//    messages when connections are established and removed from the server.

//    The application listens for TCP connections on port 5150 and accepts

//    them as they arrive. When this application receives data from a client,

//    it simply echos (this is why we call it an echo server) the data back in

//    it's original form until the client closes the connection.

//

//    Note: There are no command line options for this sample.

//

// Link to ws2_32.lib

#include <winsock2.h>

#include <windows.h>

#include <stdio.h>

 

#define PORT 5150

#define DATA_BUFSIZE 8192

 

typedef struct _SOCKET_INFORMATION {

   CHAR Buffer[DATA_BUFSIZE];

   WSABUF DataBuf;

   SOCKET Socket;

   OVERLAPPED Overlapped;

   DWORD BytesSEND;

   DWORD BytesRECV;

} SOCKET_INFORMATION, * LPSOCKET_INFORMATION;

 

// Prototypes

BOOL CreateSocketInformation(SOCKET s);

void FreeSocketInformation(DWORD Index);

 

// Global var

DWORD TotalSockets = 0;

LPSOCKET_INFORMATION SocketArray[FD_SETSIZE];

 

int main(int argc, char **argv)

{

   SOCKET ListenSocket;

   SOCKET AcceptSocket;

   SOCKADDR_IN InternetAddr;

   WSADATA wsaData;

   INT Ret;

   FD_SET WriteSet;

   FD_SET ReadSet;

   DWORD i;

   DWORD Total;

   ULONG NonBlock;

   DWORD Flags;

   DWORD SendBytes;

   DWORD RecvBytes;

 

   if ((Ret = WSAStartup(0x0202,&wsaData)) != 0)

   {

      printf("WSAStartup() failed with error %d\n", Ret);

      WSACleanup();

      return 1;

   }

   else

      printf("WSAStartup() is fine!\n");

 

   // Prepare a socket to listen for connections

   if ((ListenSocket = WSASocket(AF_INET, SOCK_STREAM, 0, NULL, 0, WSA_FLAG_OVERLAPPED)) == INVALID_SOCKET)

   {

      printf("WSASocket() failed with error %d\n", WSAGetLastError());

      return 1;

   }

   else

      printf("WSASocket() is OK!\n");

 

   InternetAddr.sin_family = AF_INET;

   InternetAddr.sin_addr.s_addr = htonl(INADDR_ANY);

   InternetAddr.sin_port = htons(PORT);

 

   if (bind(ListenSocket, (PSOCKADDR) &InternetAddr, sizeof(InternetAddr)) == SOCKET_ERROR)

   {

      printf("bind() failed with error %d\n", WSAGetLastError());

      return 1;

   }

   else

               printf("bind() is OK!\n");

 

   if (listen(ListenSocket, 5))

   {

      printf("listen() failed with error %d\n", WSAGetLastError());

      return 1;

   }

   else

               printf("listen() is OK!\n");

 

   // Change the socket mode on the listening socket from blocking to

   // non-block so the application will not block waiting for requests

   NonBlock = 1;

   if (ioctlsocket(ListenSocket, FIONBIO, &NonBlock) == SOCKET_ERROR)

   {

      printf("ioctlsocket() failed with error %d\n", WSAGetLastError());

      return 1;

   }

   else

      printf("ioctlsocket() is OK!\n");

 

   while(TRUE)

   {

      // Prepare the Read and Write socket sets for network I/O notification

      FD_ZERO(&ReadSet);

      FD_ZERO(&WriteSet);

 

      // Always look for connection attempts

      FD_SET(ListenSocket, &ReadSet);

 

      // Set Read and Write notification for each socket based on the

      // current state the buffer.  If there is data remaining in the

      // buffer then set the Write set otherwise the Read set

      for (i = 0; i < TotalSockets; i++)

         if (SocketArray[i]->BytesRECV > SocketArray[i]->BytesSEND)

            FD_SET(SocketArray[i]->Socket, &WriteSet);

         else

            FD_SET(SocketArray[i]->Socket, &ReadSet);

 

      if ((Total = select(0, &ReadSet, &WriteSet, NULL, NULL)) == SOCKET_ERROR)

      {

         printf("select() returned with error %d\n", WSAGetLastError());

         return 1;

      }

      else

         printf("select() is OK!\n");

 

      // Check for arriving connections on the listening socket.

      if (FD_ISSET(ListenSocket, &ReadSet))

      {

         Total--;

         if ((AcceptSocket = accept(ListenSocket, NULL, NULL)) != INVALID_SOCKET)

         {

            // Set the accepted socket to non-blocking mode so the server will

            // not get caught in a blocked condition on WSASends

            NonBlock = 1;

            if (ioctlsocket(AcceptSocket, FIONBIO, &NonBlock) == SOCKET_ERROR)

            {

               printf("ioctlsocket(FIONBIO) failed with error %d\n", WSAGetLastError());

               return 1;

            }

            else

               printf("ioctlsocket(FIONBIO) is OK!\n");

 

            if (CreateSocketInformation(AcceptSocket) == FALSE)

            {

                 printf("CreateSocketInformation(AcceptSocket) failed!\n");

                 return 1;

            }

            else

                printf("CreateSocketInformation() is OK!\n");

 

         }

         else

         {

            if (WSAGetLastError() != WSAEWOULDBLOCK)

            {

               printf("accept() failed with error %d\n", WSAGetLastError());

               return 1;

            }

            else

               printf("accept() is fine!\n");

         }

      }

 

      // Check each socket for Read and Write notification until the number

      // of sockets in Total is satisfied

      for (i = 0; Total > 0 && i < TotalSockets; i++)

      {

         LPSOCKET_INFORMATION SocketInfo = SocketArray[i];

 

         // If the ReadSet is marked for this socket then this means data

         // is available to be read on the socket

         if (FD_ISSET(SocketInfo->Socket, &ReadSet))

         {

            Total--;

 

            SocketInfo->DataBuf.buf = SocketInfo->Buffer;

            SocketInfo->DataBuf.len = DATA_BUFSIZE;

 

            Flags = 0;

            if (WSARecv(SocketInfo->Socket, &(SocketInfo->DataBuf), 1, &RecvBytes, &Flags, NULL, NULL) == SOCKET_ERROR)

            {

               if (WSAGetLastError() != WSAEWOULDBLOCK)

               {

                  printf("WSARecv() failed with error %d\n", WSAGetLastError());

                  FreeSocketInformation(i);

               }

               else

                  printf("WSARecv() is OK!\n");

               continue;

            }

            else

            {

               SocketInfo->BytesRECV = RecvBytes;

 

               // If zero bytes are received, this indicates the peer closed the connection.

               if (RecvBytes == 0)

               {

                  FreeSocketInformation(i);

                  continue;

               }

            }

         }

 

         // If the WriteSet is marked on this socket then this means the internal

         // data buffers are available for more data

         if (FD_ISSET(SocketInfo->Socket, &WriteSet))

         {

            Total--;

 

            SocketInfo->DataBuf.buf = SocketInfo->Buffer + SocketInfo->BytesSEND;

            SocketInfo->DataBuf.len = SocketInfo->BytesRECV - SocketInfo->BytesSEND;

 

            if (WSASend(SocketInfo->Socket, &(SocketInfo->DataBuf), 1, &SendBytes, 0, NULL, NULL) == SOCKET_ERROR)

            {

               if (WSAGetLastError() != WSAEWOULDBLOCK)

               {

                  printf("WSASend() failed with error %d\n", WSAGetLastError());

                  FreeSocketInformation(i);

               }

               else

                  printf("WSASend() is OK!\n");

 

               continue;

            }

            else

            {

               SocketInfo->BytesSEND += SendBytes;

 

               if (SocketInfo->BytesSEND == SocketInfo->BytesRECV)

               {

                  SocketInfo->BytesSEND = 0;

                  SocketInfo->BytesRECV = 0;

               }

            }

         }

      }

   }

}

 

BOOL CreateSocketInformation(SOCKET s)

{

   LPSOCKET_INFORMATION SI;

 

   printf("Accepted socket number %d\n", s);

 

   if ((SI = (LPSOCKET_INFORMATION) GlobalAlloc(GPTR, sizeof(SOCKET_INFORMATION))) == NULL)

   {

      printf("GlobalAlloc() failed with error %d\n", GetLastError());

      return FALSE;

   }

   else

      printf("GlobalAlloc() for SOCKET_INFORMATION is OK!\n");

 

   // Prepare SocketInfo structure for use

   SI->Socket = s;

   SI->BytesSEND = 0;

   SI->BytesRECV = 0;

 

   SocketArray[TotalSockets] = SI;

   TotalSockets++;

   return(TRUE);

}

 

void FreeSocketInformation(DWORD Index)

{

   LPSOCKET_INFORMATION SI = SocketArray[Index];

   DWORD i;

 

   closesocket(SI->Socket);

   printf("Closing socket number %d\n", SI->Socket);

   GlobalFree(SI);

 

   // Squash the socket array

   for (i = Index; i < TotalSockets; i++)

   {

      SocketArray[i] = SocketArray[i + 1];

   }

 

   TotalSockets--;

}

 

Build and run the project. The following screenshot is a sample output.

 

---------------------------------------------------------------

Winsock 2 socket I/O Methods: A program example demonstrates the use of select() for server/receiver program - Running the program without any argument, program is waiting for connection.

 

The Client Test Program Example

 

The following program example is a client that will be used to test all the server/receiver program created in this chapter. This program uses TCP protocol.

 

Winsock 2 socket I/O Methods: The Client Test Program Example, creating a new empty Win32 console mode application and add the project/solution name.

 

Add the following source code.

 

// Description:

//    This sample is the echo client. It connects to the TCP server,

//    sends data, and reads data back from the server.

//

// Command Line Options:

//    client [-p:x] [-s:IP] [-n:x] [-o]

//           -p:x      Remote port to send to

//           -s:IP     Server's IP address or hostname

//           -n:x      Number of times to send message

//           -o        Send messages only; don't receive

//

// Link to ws2_32.lib

#include <winsock2.h>

#include <stdio.h>

#include <stdlib.h>

 

#define DEFAULT_COUNT       20

#define DEFAULT_PORT        5150

#define DEFAULT_BUFFER      2048

#define DEFAULT_MESSAGE     "\'A test message from client\'"

 

char  szServer[128],                          // Server to connect to

      szMessage[1024];                      // Message to send to sever

int   iPort     = DEFAULT_PORT;    // Port on server to connect to

DWORD dwCount   = DEFAULT_COUNT; // Number of times to send message

BOOL  bSendOnly = FALSE;                        // Send data only; don't receive

 

// Function: usage:

// Description: Print usage information and exit

void usage()

{

    printf("Chapter5TestClient: client [-p:x] [-s:IP] [-n:x] [-o]\n\n");

    printf("       -p:x      Remote port to send to\n");

    printf("       -s:IP     Server's IP address or hostname\n");

    printf("       -n:x      Number of times to send message\n");

    printf("       -o        Send messages only; don't receive\n");

    printf("\n");

}

 

// Function: ValidateArgs

// Description:

//    Parse the command line arguments, and set some global flags

//    to indicate what actions to perform

void ValidateArgs(int argc, char **argv)

{

    int    i;

 

    for(i = 1; i < argc; i++)

    {

        if ((argv[i][0] == '-') || (argv[i][0] == '/'))

        {

            switch (tolower(argv[i][1]))

            {

                case 'p':        // Remote port

                    if (strlen(argv[i]) > 3)

                        iPort = atoi(&argv[i][3]);

                    break;

                case 's':       // Server

                    if (strlen(argv[i]) > 3)

                        strcpy_s(szServer, sizeof(szServer),&argv[i][3]);

                    break;

                case 'n':       // Number of times to send message

                    if (strlen(argv[i]) > 3)

                        dwCount = atol(&argv[i][3]);

                    break;

                case 'o':       // Only send message; don't receive

                    bSendOnly = TRUE;

                    break;

                default:

                    usage();

                    break;

            }

        }

    }

}

 

// Function: main

// Description:

//    Main thread of execution. Initialize Winsock, parse the

//    command line arguments, create a socket, connect to the

//    server, and then send and receive data.

int main(int argc, char **argv)

{

    WSADATA       wsd;

    SOCKET        sClient;

    char          szBuffer[DEFAULT_BUFFER];

    int           ret, i;

    struct sockaddr_in server;

    struct hostent    *host = NULL;

 

            if(argc < 2)

            {

                        usage();

                        exit(1);

            }

 

    // Parse the command line and load Winsock

    ValidateArgs(argc, argv);

    if (WSAStartup(MAKEWORD(2,2), &wsd) != 0)

    {

        printf("Failed to load Winsock library! Error %d\n", WSAGetLastError());

        return 1;

    }

    else

        printf("Winsock library loaded successfully!\n");

 

    strcpy_s(szMessage, sizeof(szMessage),DEFAULT_MESSAGE);

 

    // Create the socket, and attempt to connect to the server

    sClient = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

    if (sClient == INVALID_SOCKET)

    {

        printf("socket() failed with error code %d\n", WSAGetLastError());

        return 1;

    }

    else

        printf("socket() looks fine!\n");

 

    server.sin_family = AF_INET;

    server.sin_port = htons(iPort);

    server.sin_addr.s_addr = inet_addr(szServer);

 

    // If the supplied server address wasn't in the form

    // "aaa.bbb.ccc.ddd" it's a hostname, so try to resolve it

    if (server.sin_addr.s_addr == INADDR_NONE)

    {

        host = gethostbyname(szServer);

        if (host == NULL)

        {

            printf("Unable to resolve server %s\n", szServer);

            return 1;

        }

        else

            printf("The hostname resolved successfully!\n");

 

        CopyMemory(&server.sin_addr, host->h_addr_list[0], host->h_length);

    }

 

    if (connect(sClient, (struct sockaddr *)&server, sizeof(server)) == SOCKET_ERROR)

    {

        printf("connect() failed with error code %d\n", WSAGetLastError());

        return 1;

    }

    else

        printf("connect() is pretty damn fine!\n");

 

    // Send and receive data

    printf("Sending and receiving data if any...\n");

 

    for(i = 0; i < (int)dwCount; i++)

    {

        ret = send(sClient, szMessage, strlen(szMessage), 0);

        if (ret == 0)

            break;

        else if (ret == SOCKET_ERROR)

        {

            printf("send() failed with error code %d\n", WSAGetLastError());

            break;

        }

 

        printf("send() should be fine. Send %d bytes\n", ret);

        if (!bSendOnly)

        {

            ret = recv(sClient, szBuffer, DEFAULT_BUFFER, 0);

            if (ret == 0)        // Graceful close

            {

                   printf("It is a graceful close!\n");

                   break;

            }

            else if (ret == SOCKET_ERROR)

            {

                printf("recv() failed with error code %d\n", WSAGetLastError());

                break;

            }

            szBuffer[ret] = '\0';

            printf("recv() is OK. Received %d bytes: %s\n", ret, szBuffer);

           }

    }

 

    if(closesocket(sClient) == 0)

            printf("closesocket() is OK!\n");

    else

            printf("closesocket() failed with error code %d\n", WSAGetLastError());

 

    if (WSACleanup() == 0)

            printf("WSACleanup() is fine!\n");

    else

            printf("WSACleanup() failed with error code %d\n", WSAGetLastError());

 

    return 0;

}

 

Build and run the project. The following screenshot is a sample output.

 

Winsock 2 socket I/O Methods: The Client Test Program Example - a sample output of the select() client program

 

 

 


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