    // @(#)root/net:$Name:  $:$Id: TServerSocket.cxx,v 1.4 2004/02/19 00:11:18 rdm Exp $
    // Author: Fons Rademakers   18/12/96

    /*************************************************************************
     * Copyright (C) 1995-2000, Rene Brun and Fons Rademakers.               *
     * All rights reserved.                                                  *
     *                                                                       *
     * For the licensing terms see $ROOTSYS/LICENSE.                         *
     * For the list of contributors see $ROOTSYS/README/CREDITS.             *
     *************************************************************************/

    //////////////////////////////////////////////////////////////////////////
    //                                                                      //
    // TServerSocket                                                        //
    //                                                                      //
    // This class implements server sockets. A server socket waits for      //
    // requests to come in over the network. It performs some operation     //
    // based on that request and then possibly returns a full duplex socket //
    // to the requester. The actual work is done via the TSystem class      //
    // (either TUnixSystem, TWin32System or TMacSystem).                    //
    //                                                                      //
    //////////////////////////////////////////////////////////////////////////

    #include "TServerSocket.h"
    #include "TSocket.h"
    #include "TSystem.h"
    #include "TROOT.h"
    #include "TError.h"

    ClassImp(TServerSocket)

    //______________________________________________________________________________
     TServerSocket::TServerSocket(const char *service, Bool_t reuse, Int_t backlog,
                                 Int_t tcpwindowsize)
    {
       // Create a server socket object for a named service. Set reuse to true
       // to force reuse of the server socket (i.e. do not wait for the time
       // out to pass). Using backlog one can set the desirable queue length
       // for pending connections.
       // Use tcpwindowsize to specify the size of the receive buffer, it has
       // to be specified here to make sure the window scale option is set (for
       // tcpwindowsize > 65KB and for platforms supporting window scaling).
       // Use IsValid() to check the validity of the
       // server socket. In case server socket is not valid use GetErrorCode()
       // to obtain the specific error value. These values are:
       //  0 = no error (socket is valid)
       // -1 = low level socket() call failed
       // -2 = low level bind() call failed
       // -3 = low level listen() call failed
       // Every valid server socket is added to the TROOT sockets list which
       // will make sure that any open sockets are properly closed on
       // program termination.

       Assert(gROOT);
       Assert(gSystem);

       SetName("ServerSocket");

       fSecContext = 0;
       int port = gSystem->GetServiceByName(service);
       fService = service;

       if (port != -1) {
          fSocket = gSystem->AnnounceTcpService(port, reuse, backlog, tcpwindowsize);
          if (fSocket >= 0) gROOT->GetListOfSockets()->Add(this);
       } else
          fSocket = -1;
    }

    //______________________________________________________________________________
     TServerSocket::TServerSocket(Int_t port, Bool_t reuse, Int_t backlog,
                                 Int_t tcpwindowsize)
    {
       // Create a server socket object on a specified port. Set reuse to true
       // to force reuse of the server socket (i.e. do not wait for the time
       // out to pass). Using backlog one can set the desirable queue length
       // for pending connections. If port is 0 a port scan will be done to
       // find a free port. This option is mutual exlusive with the reuse option.
       // Use tcpwindowsize to specify the size of the receive buffer, it has
       // to be specified here to make sure the window scale option is set (for
       // tcpwindowsize > 65KB and for platforms supporting window scaling).
       // Use IsValid() to check the validity of the
       // server socket. In case server socket is not valid use GetErrorCode()
       // to obtain the specific error value. These values are:
       //  0 = no error (socket is valid)
       // -1 = low level socket() call failed
       // -2 = low level bind() call failed
       // -3 = low level listen() call failed
       // Every valid server socket is added to the TROOT sockets list which
       // will make sure that any open sockets are properly closed on
       // program termination.

       Assert(gROOT);
       Assert(gSystem);

       SetName("ServerSocket");

       fSecContext = 0;
       fService = gSystem->GetServiceByPort(port);
       SetTitle(fService);

       fSocket = gSystem->AnnounceTcpService(port, reuse, backlog, tcpwindowsize);
       if (fSocket >= 0) gROOT->GetListOfSockets()->Add(this);
    }

    //______________________________________________________________________________
     TSocket *TServerSocket::Accept()
    {
       // Accept a connection on a server socket. Returns a full-duplex
       // communication TSocket object. If no pending connections are
       // present on the queue and nonblocking mode has not been enabled
       // with SetOption(kNoBlock,1) the call blocks until a connection is
       // present. The returned socket must be deleted by the user. The socket
       // is also added to the TROOT sockets list which will make sure that
       // any open sockets are properly closed on program termination.
       // In case of error 0 is returned and in case non-blocking I/O is
       // enabled and no connections are available -1 is returned.

       if (fSocket == -1) { return 0; }

       TSocket *socket = new TSocket;

       Int_t soc = gSystem->AcceptConnection(fSocket);
       if (soc == -1) { delete socket; return 0; }
       if (soc == -2) { delete socket; return (TSocket*) -1; }

       socket->fSocket  = soc;
       socket->fSecContext = 0;
       socket->fService = fService;
       socket->fAddress = gSystem->GetPeerName(socket->fSocket);
       if (socket->fSocket >= 0) gROOT->GetListOfSockets()->Add(socket);

       return socket;
    }

    //______________________________________________________________________________
     TInetAddress TServerSocket::GetLocalInetAddress()
    {
       // Return internet address of host to which the server socket is bound,
       // i.e. the local host. In case of error TInetAddress::IsValid() returns
       // kFALSE.

       if (fSocket != -1) {
          if (fAddress.GetPort() == -1)
             fAddress = gSystem->GetSockName(fSocket);
          return fAddress;
       }
       return TInetAddress();
    }

    //______________________________________________________________________________
     Int_t TServerSocket::GetLocalPort()
    {
       // Get port # to which server socket is bound. In case of error returns -1.

       if (fSocket != -1) {
          if (fAddress.GetPort() == -1)
             fAddress = GetLocalInetAddress();
          return fAddress.GetPort();
       }
       return -1;
    }