// @(#)root/net:$Id: TUDPSocket.cxx 41908 2011-11-11 14:43:28Z pcanal $
// Author: Marcelo Sousa   26/10/2011

/*************************************************************************
 * Copyright (C) 1995-2011, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/

//////////////////////////////////////////////////////////////////////////
//                                                                      //
// TUDPSocket                                                           //
//                                                                      //
// This class implements UDP client sockets. A socket is an endpoint    //
// for communication between two machines.                              //
// The actual work is done via the TSystem class (either TUnixSystem    //
// or TWinNTSystem).                                                    //
//                                                                      //
//////////////////////////////////////////////////////////////////////////

#include "Bytes.h"
#include "Compression.h"
#include "NetErrors.h"
#include "TEnv.h"
#include "TError.h"
#include "TMessage.h"
#include "TUDPSocket.h"
#include "TPluginManager.h"
#include "TROOT.h"
#include "TString.h"
#include "TSystem.h"
#include "TUrl.h"
#include "TVirtualAuth.h"
#include "TStreamerInfo.h"
#include "TProcessID.h"

ULong64_t TUDPSocket::fgBytesSent = 0;
ULong64_t TUDPSocket::fgBytesRecv = 0;


ClassImp(TUDPSocket)

//______________________________________________________________________________
TUDPSocket::TUDPSocket(TInetAddress addr, const char *service)
         : TNamed(addr.GetHostName(), service)
{
   // Create a socket. Connect to the named service at address addr.
   // 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).
   // Returns when connection has been accepted by remote side. Use IsValid()
   // to check the validity of the socket. Every socket is added to the TROOT
   // sockets list which will make sure that any open sockets are properly
   // closed on program termination.

   R__ASSERT(gROOT);
   R__ASSERT(gSystem);

   fService = service;
   fSecContext = 0;
   fRemoteProtocol= -1;
   fServType = kSOCKD;
   if (fService.Contains("root"))
      fServType = kROOTD;
   if (fService.Contains("proof"))
      fServType = kPROOFD;
   fAddress = addr;
   fAddress.fPort = gSystem->GetServiceByName(service);
   fBytesSent = 0;
   fBytesRecv = 0;
   fCompress = 0;
   fUUIDs = 0;
   fLastUsageMtx = 0;
   ResetBit(TUDPSocket::kBrokenConn);

   if (fAddress.GetPort() != -1) {
      fSocket = gSystem->OpenConnection(addr.GetHostName(), fAddress.GetPort(),
                                        -1, "upd");

      if (fSocket != -1) {
         R__LOCKGUARD2(gROOTMutex);
         gROOT->GetListOfSockets()->Add(this);
      }
   } else
      fSocket = -1;

}


//______________________________________________________________________________
TUDPSocket::TUDPSocket(TInetAddress addr, Int_t port)
         : TNamed(addr.GetHostName(), "")
{
   // Create a socket. Connect to the specified port # at address addr.
   // 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).
   // Returns when connection has been accepted by remote side. Use IsValid()
   // to check the validity of the socket. Every socket is added to the TROOT
   // sockets list which will make sure that any open sockets are properly
   // closed on program termination.

   R__ASSERT(gROOT);
   R__ASSERT(gSystem);

   fService = gSystem->GetServiceByPort(port);
   fSecContext = 0;
   fRemoteProtocol= -1;
   fServType = kSOCKD;
   if (fService.Contains("root"))
      fServType = kROOTD;
   if (fService.Contains("proof"))
      fServType = kPROOFD;
   fAddress = addr;
   fAddress.fPort = port;
   SetTitle(fService);
   fBytesSent = 0;
   fBytesRecv = 0;
   fCompress = 0;
   fUUIDs = 0;
   fLastUsageMtx = 0;
   ResetBit(TUDPSocket::kBrokenConn);

   fSocket = gSystem->OpenConnection(addr.GetHostName(), fAddress.GetPort(),
                                     -1, "upd");
   if (fSocket == -1)
      fAddress.fPort = -1;
   else {
      R__LOCKGUARD2(gROOTMutex);
      gROOT->GetListOfSockets()->Add(this);
   }
}

//______________________________________________________________________________
TUDPSocket::TUDPSocket(const char *host, const char *service)
         : TNamed(host, service)
{
   // Create a socket. Connect to named service on the remote host.
   // 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).
   // Returns when connection has been accepted by remote side. Use IsValid()
   // to check the validity of the socket. Every socket is added to the TROOT
   // sockets list which will make sure that any open sockets are properly
   // closed on program termination.

   R__ASSERT(gROOT);
   R__ASSERT(gSystem);

   fService = service;
   fSecContext = 0;
   fRemoteProtocol= -1;
   fServType = kSOCKD;
   if (fService.Contains("root"))
      fServType = kROOTD;
   if (fService.Contains("proof"))
      fServType = kPROOFD;
   fAddress = gSystem->GetHostByName(host);
   fAddress.fPort = gSystem->GetServiceByName(service);
   SetName(fAddress.GetHostName());
   fBytesSent = 0;
   fBytesRecv = 0;
   fCompress = 0;
   fUUIDs = 0;
   fLastUsageMtx = 0;
   ResetBit(TUDPSocket::kBrokenConn);

   if (fAddress.GetPort() != -1) {
      fSocket = gSystem->OpenConnection(host, fAddress.GetPort(), -1, "upd");
      if (fSocket != -1) {
         R__LOCKGUARD2(gROOTMutex);
         gROOT->GetListOfSockets()->Add(this);
      }
   } else
      fSocket = -1;
}

//______________________________________________________________________________
TUDPSocket::TUDPSocket(const char *url, Int_t port)
         : TNamed(TUrl(url).GetHost(), "")
{
   // Create a socket; see CreateAuthSocket for the form of url.
   // Connect to the specified port # on the remote host.
   // If user is specified in url, try authentication as user.
   // 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).
   // Returns when connection has been accepted by remote side. Use IsValid()
   // to check the validity of the socket. Every socket is added to the TROOT
   // sockets list which will make sure that any open sockets are properly
   // closed on program termination.

   R__ASSERT(gROOT);
   R__ASSERT(gSystem);

   fUrl = TString(url);
   TString host(TUrl(fUrl).GetHost());

   fService = gSystem->GetServiceByPort(port);
   fSecContext = 0;
   fRemoteProtocol= -1;
   fServType = kSOCKD;
   if (fUrl.Contains("root"))
      fServType = kROOTD;
   if (fUrl.Contains("proof"))
      fServType = kPROOFD;
   fAddress = gSystem->GetHostByName(host);
   fAddress.fPort = port;
   SetName(fAddress.GetHostName());
   SetTitle(fService);
   fBytesSent = 0;
   fBytesRecv = 0;
   fCompress = 0;
   fUUIDs = 0;
   fLastUsageMtx = 0;
   ResetBit(TUDPSocket::kBrokenConn);

   fSocket = gSystem->OpenConnection(host, fAddress.GetPort(), -1, "udp");
   if (fSocket == -1) {
      fAddress.fPort = -1;
   } else {
      R__LOCKGUARD2(gROOTMutex);
      gROOT->GetListOfSockets()->Add(this);
   }
}

//______________________________________________________________________________
TUDPSocket::TUDPSocket(const char *sockpath) : TNamed(sockpath, "")
{
   // Create a socket in the Unix domain on 'sockpath'.
   // Returns when connection has been accepted by the server. Use IsValid()
   // to check the validity of the socket. Every socket is added to the TROOT
   // sockets list which will make sure that any open sockets are properly
   // closed on program termination.

   R__ASSERT(gROOT);
   R__ASSERT(gSystem);

   fUrl = sockpath;

   fService = "unix";
   fSecContext = 0;
   fRemoteProtocol= -1;
   fServType = kSOCKD;
   fAddress.fPort = -1;
   fName.Form("unix:%s", sockpath);
   SetTitle(fService);
   fBytesSent = 0;
   fBytesRecv = 0;
   fCompress  = 0;
   fUUIDs = 0;
   fLastUsageMtx  = 0;
   ResetBit(TUDPSocket::kBrokenConn);

   fSocket = gSystem->OpenConnection(sockpath, -1, -1, "udp");
   if (fSocket > 0) {
      R__LOCKGUARD2(gROOTMutex);
      gROOT->GetListOfSockets()->Add(this);
   }
}

//______________________________________________________________________________
TUDPSocket::TUDPSocket(Int_t desc) : TNamed("", "")
{
   // Create a socket. The socket will adopt previously opened TCP socket with
   // descriptor desc.

   R__ASSERT(gROOT);
   R__ASSERT(gSystem);

   fSecContext     = 0;
   fRemoteProtocol = 0;
   fService        = (char *)kSOCKD;
   fServType       = kSOCKD;
   fBytesSent      = 0;
   fBytesRecv      = 0;
   fCompress       = 0;
   fUUIDs          = 0;
   fLastUsageMtx   = 0;
   ResetBit(TUDPSocket::kBrokenConn);

   if (desc >= 0) {
      fSocket  = desc;
      fAddress = gSystem->GetPeerName(fSocket);
      R__LOCKGUARD2(gROOTMutex);
      gROOT->GetListOfSockets()->Add(this);
   } else
      fSocket = -1;
}

//______________________________________________________________________________
TUDPSocket::TUDPSocket(Int_t desc, const char *sockpath) : TNamed(sockpath, "")
{
   // Create a socket. The socket will adopt previously opened Unix socket with
   // descriptor desc. The sockpath arg is for info purposes only. Use
   // this method to adopt e.g. a socket created via socketpair().

   R__ASSERT(gROOT);
   R__ASSERT(gSystem);

   fUrl = sockpath;

   fService = "unix";
   fSecContext = 0;
   fRemoteProtocol= -1;
   fServType = kSOCKD;
   fAddress.fPort = -1;
   fName.Form("unix:%s", sockpath);
   SetTitle(fService);
   fBytesSent = 0;
   fBytesRecv = 0;
   fCompress  = 0;
   fUUIDs = 0;
   fLastUsageMtx  = 0;
   ResetBit(TUDPSocket::kBrokenConn);

   if (desc >= 0) {
      fSocket  = desc;
      R__LOCKGUARD2(gROOTMutex);
      gROOT->GetListOfSockets()->Add(this);
   } else
      fSocket = -1;
}


//______________________________________________________________________________
TUDPSocket::TUDPSocket(const TUDPSocket &s) : TNamed(s)
{
   // TUDPSocket copy ctor.

   fSocket         = s.fSocket;
   fService        = s.fService;
   fAddress        = s.fAddress;
   fLocalAddress   = s.fLocalAddress;
   fBytesSent      = s.fBytesSent;
   fBytesRecv      = s.fBytesRecv;
   fCompress       = s.fCompress;
   fSecContext     = s.fSecContext;
   fRemoteProtocol = s.fRemoteProtocol;
   fServType       = s.fServType;
   fUUIDs          = 0;
   fLastUsageMtx   = 0;
   ResetBit(TUDPSocket::kBrokenConn);

   if (fSocket != -1) {
      R__LOCKGUARD2(gROOTMutex);
      gROOT->GetListOfSockets()->Add(this);
   }
}

//______________________________________________________________________________
void TUDPSocket::Close(Option_t *option)
{
   // Close the socket. If option is "force", calls shutdown(id,2) to
   // shut down the connection. This will close the connection also
   // for the parent of this process. Also called via the dtor (without
   // option "force", call explicitely Close("force") if this is desired).

   Bool_t force = option ? (!strcmp(option, "force") ? kTRUE : kFALSE) : kFALSE;

   if (fSocket != -1) {
      gSystem->CloseConnection(fSocket, force);
      R__LOCKGUARD2(gROOTMutex);
      gROOT->GetListOfSockets()->Remove(this);
   }
   fSocket = -1;

   SafeDelete(fUUIDs);
   SafeDelete(fLastUsageMtx);
}

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

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

//______________________________________________________________________________
Int_t TUDPSocket::GetLocalPort()
{
   // Return the local port # to which the socket is bound.
   // In case of error return -1.

   if (IsValid()) {
      if (fLocalAddress.GetPort() == -1)
         GetLocalInetAddress();
      return fLocalAddress.GetPort();
   }
   return -1;
}

//______________________________________________________________________________
Int_t TUDPSocket::Select(Int_t interest, Long_t timeout)
{
   // Waits for this socket to change status. If interest=kRead,
   // the socket will be watched to see if characters become available for
   // reading; if interest=kWrite the socket will be watched to
   // see if a write will not block.
   // The argument 'timeout' specifies a maximum time to wait in millisec.
   // Default no timeout.
   // Returns 1 if a change of status of interest has been detected within
   // timeout; 0 in case of timeout; < 0 if an error occured.

   Int_t rc = 1;

   // Associate a TFileHandler to this socket
   TFileHandler fh(fSocket, interest);

   // Wait for an event now
   rc = gSystem->Select(&fh, timeout);

   return rc;
}

//______________________________________________________________________________
Int_t TUDPSocket::Send(Int_t kind)
{
   // Send a single message opcode. Use kind (opcode) to set the
   // TMessage "what" field. Returns the number of bytes that were sent
   // (always sizeof(Int_t)) and -1 in case of error. In case the kind has
   // been or'ed with kMESS_ACK, the call will only return after having
   // received an acknowledgement, making the sending process synchronous.

   TMessage mess(kind);

   Int_t nsent;
   if ((nsent = Send(mess)) < 0)
      return -1;

   return nsent;
}

//______________________________________________________________________________
Int_t TUDPSocket::Send(Int_t status, Int_t kind)
{
   // Send a status and a single message opcode. Use kind (opcode) to set the
   // TMessage "what" field. Returns the number of bytes that were sent
   // (always 2*sizeof(Int_t)) and -1 in case of error. In case the kind has
   // been or'ed with kMESS_ACK, the call will only return after having
   // received an acknowledgement, making the sending process synchronous.

   TMessage mess(kind);
   mess << status;

   Int_t nsent;
   if ((nsent = Send(mess)) < 0)
      return -1;

   return nsent;
}

//______________________________________________________________________________
Int_t TUDPSocket::Send(const char *str, Int_t kind)
{
   // Send a character string buffer. Use kind to set the TMessage "what" field.
   // Returns the number of bytes in the string str that were sent and -1 in
   // case of error. In case the kind has been or'ed with kMESS_ACK, the call
   // will only return after having received an acknowledgement, making the
   // sending process synchronous.

   TMessage mess(kind);
   if (str) mess.WriteString(str);

   Int_t nsent;
   if ((nsent = Send(mess)) < 0)
      return -1;

   return nsent - sizeof(Int_t);    // - TMessage::What()
}

//______________________________________________________________________________
Int_t TUDPSocket::Send(const TMessage &mess)
{
   // Send a TMessage object. Returns the number of bytes in the TMessage
   // that were sent and -1 in case of error. In case the TMessage::What
   // has been or'ed with kMESS_ACK, the call will only return after having
   // received an acknowledgement, making the sending process synchronous.
   // Returns -4 in case of kNoBlock and errno == EWOULDBLOCK.
   // Returns -5 if pipe broken or reset by peer (EPIPE || ECONNRESET).
   // support for streaming TStreamerInfo added by Rene Brun May 2008
   // support for streaming TProcessID added by Rene Brun June 2008

   TSystem::ResetErrno();

   if (fSocket == -1) return -1;

   if (mess.IsReading()) {
      Error("Send", "cannot send a message used for reading");
      return -1;
   }

   // send streamer infos in case schema evolution is enabled in the TMessage
   SendStreamerInfos(mess);

   // send the process id's so TRefs work
   SendProcessIDs(mess);

   mess.SetLength();   //write length in first word of buffer

   if (GetCompressionLevel() > 0 && mess.GetCompressionLevel() == 0)
      const_cast<TMessage&>(mess).SetCompressionSettings(fCompress);

   if (mess.GetCompressionLevel() > 0)
      const_cast<TMessage&>(mess).Compress();

   char *mbuf = mess.Buffer();
   Int_t mlen = mess.Length();
   if (mess.CompBuffer()) {
      mbuf = mess.CompBuffer();
      mlen = mess.CompLength();
   }

   ResetBit(TUDPSocket::kBrokenConn);
   Int_t nsent;
   if ((nsent = gSystem->SendRaw(fSocket, mbuf, mlen, 0)) <= 0) {
      if (nsent == -5) {
         // Connection reset by peer or broken
         SetBit(TUDPSocket::kBrokenConn);
         Close();
      }
      return nsent;
   }

   fBytesSent  += nsent;
   fgBytesSent += nsent;

   // If acknowledgement is desired, wait for it
   if (mess.What() & kMESS_ACK) {
      TSystem::ResetErrno();
      ResetBit(TUDPSocket::kBrokenConn);
      char buf[2];
      Int_t n = 0;
      if ((n = gSystem->RecvRaw(fSocket, buf, sizeof(buf), 0)) < 0) {
         if (n == -5) {
            // Connection reset by peer or broken
            SetBit(TUDPSocket::kBrokenConn);
            Close();
         } else
            n = -1;
         return n;
      }
      if (strncmp(buf, "ok", 2)) {
         Error("Send", "bad acknowledgement");
         return -1;
      }
      fBytesRecv  += 2;
      fgBytesRecv += 2;
   }

   Touch();  // update usage timestamp

   return nsent - sizeof(UInt_t);  //length - length header
}

//______________________________________________________________________________
Int_t TUDPSocket::SendObject(const TObject *obj, Int_t kind)
{
   // Send an object. Returns the number of bytes sent and -1 in case of error.
   // In case the "kind" has been or'ed with kMESS_ACK, the call will only
   // return after having received an acknowledgement, making the sending
   // synchronous.

   //stream object to message buffer
   TMessage mess(kind);
   mess.WriteObject(obj);

   //now sending the object itself
   Int_t nsent;
   if ((nsent = Send(mess)) < 0)
      return -1;

   return nsent;
}

//______________________________________________________________________________
Int_t TUDPSocket::SendRaw(const void *buffer, Int_t length, ESendRecvOptions opt)
{
   // Send a raw buffer of specified length. Using option kOob one can send
   // OOB data. Returns the number of bytes sent or -1 in case of error.
   // Returns -4 in case of kNoBlock and errno == EWOULDBLOCK.
   // Returns -5 if pipe broken or reset by peer (EPIPE || ECONNRESET).

   TSystem::ResetErrno();

   if (fSocket == -1) return -1;

   ResetBit(TUDPSocket::kBrokenConn);
   Int_t nsent;
   if ((nsent = gSystem->SendRaw(fSocket, buffer, length, (int) opt)) <= 0) {
      if (nsent == -5) {
         // Connection reset or broken: close
         SetBit(TUDPSocket::kBrokenConn);
         Close();
      }
      return nsent;
   }

   fBytesSent  += nsent;
   fgBytesSent += nsent;

   Touch();  // update usage timestamp

   return nsent;
}

//______________________________________________________________________________
void TUDPSocket::SendStreamerInfos(const TMessage &mess)
{
   // Check if TStreamerInfo must be sent. The list of TStreamerInfo of classes
   // in the object in the message is in the fInfos list of the message.
   // We send only the TStreamerInfos not yet sent on this socket.

   if (mess.fInfos && mess.fInfos->GetEntries()) {
      TIter next(mess.fInfos);
      TStreamerInfo *info;
      TList *minilist = 0;
      while ((info = (TStreamerInfo*)next())) {
         Int_t uid = info->GetNumber();
         if (fBitsInfo.TestBitNumber(uid))
            continue; //TStreamerInfo had already been sent
         fBitsInfo.SetBitNumber(uid);
         if (!minilist)
            minilist = new TList();
         if (gDebug > 0)
            Info("SendStreamerInfos", "sending TStreamerInfo: %s, version = %d",
                 info->GetName(),info->GetClassVersion());
         minilist->Add(info);
      }
      if (minilist) {
         TMessage messinfo(kMESS_STREAMERINFO);
         messinfo.WriteObject(minilist);
         delete minilist;
         if (messinfo.fInfos)
            messinfo.fInfos->Clear();
         if (Send(messinfo) < 0)
            Warning("SendStreamerInfos", "problems sending TStreamerInfo's ...");
      }
   }
}

//______________________________________________________________________________
void TUDPSocket::SendProcessIDs(const TMessage &mess)
{
   // Check if TProcessIDs must be sent. The list of TProcessIDs
   // in the object in the message is found by looking in the TMessage bits.
   // We send only the TProcessIDs not yet send on this socket.

   if (mess.TestBitNumber(0)) {
      TObjArray *pids = TProcessID::GetPIDs();
      Int_t npids = pids->GetEntries();
      TProcessID *pid;
      TList *minilist = 0;
      for (Int_t ipid = 0; ipid < npids; ipid++) {
         pid = (TProcessID*)pids->At(ipid);
         if (!pid || !mess.TestBitNumber(pid->GetUniqueID()+1))
            continue;
         //check if a pid with this title has already been sent through the socket
         //if not add it to the fUUIDs list
         if (!fUUIDs) {
            fUUIDs = new TList();
         } else {
            if (fUUIDs->FindObject(pid->GetTitle()))
               continue;
         }
         fUUIDs->Add(new TObjString(pid->GetTitle()));
         if (!minilist)
            minilist = new TList();
         if (gDebug > 0)
            Info("SendProcessIDs", "sending TProcessID: %s", pid->GetTitle());
         minilist->Add(pid);
      }
      if (minilist) {
         TMessage messpid(kMESS_PROCESSID);
         messpid.WriteObject(minilist);
         delete minilist;
         if (Send(messpid) < 0)
            Warning("SendProcessIDs", "problems sending TProcessID's ...");
      }
   }
}

//______________________________________________________________________________
Int_t TUDPSocket::Recv(char *str, Int_t max)
{
   // Receive a character string message of maximum max length. The expected
   // message must be of type kMESS_STRING. Returns length of received string
   // (can be 0 if otherside of connection is closed) or -1 in case of error
   // or -4 in case a non-blocking socket would block (i.e. there is nothing
   // to be read).

   Int_t n, kind;

   ResetBit(TUDPSocket::kBrokenConn);
   if ((n = Recv(str, max, kind)) <= 0) {
      if (n == -5) {
         SetBit(TUDPSocket::kBrokenConn);
         n = -1;
      }
      return n;
   }

   if (kind != kMESS_STRING) {
      Error("Recv", "got message of wrong kind (expected %d, got %d)",
            kMESS_STRING, kind);
      return -1;
   }

   return n;
}

//______________________________________________________________________________
Int_t TUDPSocket::Recv(char *str, Int_t max, Int_t &kind)
{
   // Receive a character string message of maximum max length. Returns in
   // kind the message type. Returns length of received string+4 (can be 0 if
   // other side of connection is closed) or -1 in case of error or -4 in
   // case a non-blocking socket would block (i.e. there is nothing to be read).

   Int_t     n;
   TMessage *mess;

   ResetBit(TUDPSocket::kBrokenConn);
   if ((n = Recv(mess)) <= 0) {
      if (n == -5) {
         SetBit(TUDPSocket::kBrokenConn);
         n = -1;
      }
      return n;
   }

   kind = mess->What();
   if (str) {
      if (mess->BufferSize() > (Int_t)sizeof(Int_t)) // if mess contains more than kind
         mess->ReadString(str, max);
      else
         str[0] = 0;
   }

   delete mess;

   return n;   // number of bytes read (len of str + sizeof(kind)
}

//______________________________________________________________________________
Int_t TUDPSocket::Recv(Int_t &status, Int_t &kind)
{
   // Receives a status and a message type. Returns length of received
   // integers, 2*sizeof(Int_t) (can be 0 if other side of connection
   // is closed) or -1 in case of error or -4 in case a non-blocking
   // socket would block (i.e. there is nothing to be read).

   Int_t     n;
   TMessage *mess;

   ResetBit(TUDPSocket::kBrokenConn);
   if ((n = Recv(mess)) <= 0) {
      if (n == -5) {
         SetBit(TUDPSocket::kBrokenConn);
         n = -1;
      }
      return n;
   }

   kind = mess->What();
   (*mess) >> status;

   delete mess;

   return n;   // number of bytes read (2 * sizeof(Int_t)
}

//______________________________________________________________________________
Int_t TUDPSocket::Recv(TMessage *&mess)
{
   // Receive a TMessage object. The user must delete the TMessage object.
   // Returns length of message in bytes (can be 0 if other side of connection
   // is closed) or -1 in case of error or -4 in case a non-blocking socket
   // would block (i.e. there is nothing to be read) or -5 if pipe broken
   // or reset by peer (EPIPE || ECONNRESET). In those case mess == 0.

   TSystem::ResetErrno();

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

oncemore:
   ResetBit(TUDPSocket::kBrokenConn);
   Int_t  n;
   UInt_t len;
   if ((n = gSystem->RecvRaw(fSocket, &len, sizeof(UInt_t), 0)) <= 0) {
      if (n == 0 || n == -5) {
         // Connection closed, reset or broken
         SetBit(TUDPSocket::kBrokenConn);
         Close();
      }
      mess = 0;
      return n;
   }
   len = net2host(len);  //from network to host byte order

   ResetBit(TUDPSocket::kBrokenConn);
   char *buf = new char[len+sizeof(UInt_t)];
   if ((n = gSystem->RecvRaw(fSocket, buf+sizeof(UInt_t), len, 0)) <= 0) {
      if (n == 0 || n == -5) {
         // Connection closed, reset or broken
         SetBit(TUDPSocket::kBrokenConn);
         Close();
      }
      delete [] buf;
      mess = 0;
      return n;
   }

   fBytesRecv  += n + sizeof(UInt_t);
   fgBytesRecv += n + sizeof(UInt_t);

   mess = new TMessage(buf, len+sizeof(UInt_t));

   // receive any streamer infos
   if (RecvStreamerInfos(mess))
      goto oncemore;

   // receive any process ids
   if (RecvProcessIDs(mess))
      goto oncemore;

   if (mess->What() & kMESS_ACK) {
      ResetBit(TUDPSocket::kBrokenConn);
      char ok[2] = { 'o', 'k' };
      Int_t n2 = 0;
      if ((n2 = gSystem->SendRaw(fSocket, ok, sizeof(ok), 0)) < 0) {
         if (n2 == -5) {
            // Connection reset or broken
            SetBit(TUDPSocket::kBrokenConn);
            Close();
         }
         delete mess;
         mess = 0;
         return n2;
      }
      mess->SetWhat(mess->What() & ~kMESS_ACK);

      fBytesSent  += 2;
      fgBytesSent += 2;
   }

   Touch();  // update usage timestamp

   return n;
}

//______________________________________________________________________________
Int_t TUDPSocket::RecvRaw(void *buffer, Int_t length, ESendRecvOptions opt)
{
   // Receive a raw buffer of specified length bytes. Using option kPeek
   // one can peek at incoming data. Returns number of received bytes.
   // Returns -1 in case of error. In case of opt == kOob: -2 means
   // EWOULDBLOCK and -3 EINVAL. In case of non-blocking mode (kNoBlock)
   // -4 means EWOULDBLOCK. Returns -5 if pipe broken or reset by
   // peer (EPIPE || ECONNRESET).

   TSystem::ResetErrno();

   if (fSocket == -1) return -1;
   if (length == 0) return 0;

   ResetBit(TUDPSocket::kBrokenConn);
   Int_t n;
   if ((n = gSystem->RecvRaw(fSocket, buffer, length, (int) opt)) <= 0) {
      if (n == 0 || n == -5) {
         // Connection closed, reset or broken
         SetBit(TUDPSocket::kBrokenConn);
         Close();
      }
      return n;
   }

   fBytesRecv  += n;
   fgBytesRecv += n;

   Touch();  // update usage timestamp

   return n;
}

//______________________________________________________________________________
Bool_t TUDPSocket::RecvStreamerInfos(TMessage *mess)
{
   // Receive a message containing streamer infos. In case the message contains
   // streamer infos they are imported, the message will be deleted and the
   // method returns kTRUE.

   if (mess->What() == kMESS_STREAMERINFO) {
      TList *list = (TList*)mess->ReadObject(TList::Class());
      TIter next(list);
      TStreamerInfo *info;
      TObjLink *lnk = list->FirstLink();
      // First call BuildCheck for regular class
      while (lnk) {
         info = (TStreamerInfo*)lnk->GetObject();
         TObject *element = info->GetElements()->UncheckedAt(0);
         Bool_t isstl = element && strcmp("This",element->GetName())==0;
         if (!isstl) {
            info->BuildCheck();
            if (gDebug > 0)
               Info("RecvStreamerInfos", "importing TStreamerInfo: %s, version = %d",
                    info->GetName(), info->GetClassVersion());
         }
         lnk = lnk->Next();
      }
      // Then call BuildCheck for stl class
      lnk = list->FirstLink();
      while (lnk) {
         info = (TStreamerInfo*)lnk->GetObject();
         TObject *element = info->GetElements()->UncheckedAt(0);
         Bool_t isstl = element && strcmp("This",element->GetName())==0;
         if (isstl) {
            info->BuildCheck();
            if (gDebug > 0)
               Info("RecvStreamerInfos", "importing TStreamerInfo: %s, version = %d",
                    info->GetName(), info->GetClassVersion());
         }
         lnk = lnk->Next();
     }
      delete list;
      delete mess;

      return kTRUE;
   }
   return kFALSE;
}

//______________________________________________________________________________
Bool_t TUDPSocket::RecvProcessIDs(TMessage *mess)
{
   // Receive a message containing process ids. In case the message contains
   // process ids they are imported, the message will be deleted and the
   // method returns kTRUE.

   if (mess->What() == kMESS_PROCESSID) {
      TList *list = (TList*)mess->ReadObject(TList::Class());
      TIter next(list);
      TProcessID *pid;
      while ((pid = (TProcessID*)next())) {
         // check that a similar pid is not already registered in fgPIDs
         TObjArray *pidslist = TProcessID::GetPIDs();
         TIter nextpid(pidslist);
         TProcessID *p;
         while ((p = (TProcessID*)nextpid())) {
            if (!strcmp(p->GetTitle(), pid->GetTitle())) {
               delete pid;
               pid = 0;
               break;
            }
         }
         if (pid) {
            if (gDebug > 0)
               Info("RecvProcessIDs", "importing TProcessID: %s", pid->GetTitle());
            pid->IncrementCount();
            pidslist->Add(pid);
            Int_t ind = pidslist->IndexOf(pid);
            pid->SetUniqueID((UInt_t)ind);
         }
      }
      delete list;
      delete mess;

      return kTRUE;
   }
   return kFALSE;
}

//______________________________________________________________________________
Int_t TUDPSocket::SetOption(ESockOptions opt, Int_t val)
{
   // Set socket options.

   if (fSocket == -1) return -1;

   return gSystem->SetSockOpt(fSocket, opt, val);
}

//______________________________________________________________________________
Int_t TUDPSocket::GetOption(ESockOptions opt, Int_t &val)
{
   // Get socket options. Returns -1 in case of error.

   if (fSocket == -1) return -1;

   return gSystem->GetSockOpt(fSocket, opt, &val);
}

//______________________________________________________________________________
Int_t TUDPSocket::GetErrorCode() const
{
   // Returns error code. Meaning depends on context where it is called.
   // If no error condition returns 0 else a value < 0.
   // For example see TServerSocket ctor.

   if (!IsValid())
      return fSocket;

   return 0;
}

//______________________________________________________________________________
void TUDPSocket::SetCompressionAlgorithm(Int_t algorithm)
{
   // See comments for function SetCompressionSettings
   if (algorithm < 0 || algorithm >= ROOT::kUndefinedCompressionAlgorithm) algorithm = 0;
   if (fCompress < 0) {
      // if the level is not defined yet use 1 as a default
      fCompress = 100 * algorithm + 1;
   } else {
      int level = fCompress % 100;
      fCompress = 100 * algorithm + level;
   }
}

//______________________________________________________________________________
void TUDPSocket::SetCompressionLevel(Int_t level)
{
   // See comments for function SetCompressionSettings
   if (level < 0) level = 0;
   if (level > 99) level = 99;
   if (fCompress < 0) {
      // if the algorithm is not defined yet use 0 as a default
      fCompress = level;
   } else {
      int algorithm = fCompress / 100;
      if (algorithm >= ROOT::kUndefinedCompressionAlgorithm) algorithm = 0;
      fCompress = 100 * algorithm + level;
   }
}

//______________________________________________________________________________
void TUDPSocket::SetCompressionSettings(Int_t settings)
{
   // Used to specify the compression level and algorithm:
   //  settings = 100 * algorithm + level
   //
   //  level = 0, objects written to this file will not be compressed.
   //  level = 1, minimal compression level but fast.
   //  ....
   //  level = 9, maximal compression level but slower and might use more memory.
   // (For the currently supported algorithms, the maximum level is 9)
   // If compress is negative it indicates the compression level is not set yet.
   //
   // The enumeration ROOT::ECompressionAlgorithm associates each
   // algorithm with a number. There is a utility function to help
   // to set the value of the argument. For example,
   //   ROOT::CompressionSettings(ROOT::kLZMA, 1)
   // will build an integer which will set the compression to use
   // the LZMA algorithm and compression level 1.  These are defined
   // in the header file Compression.h.
   //
   // Note that the compression settings may be changed at any time.
   // The new compression settings will only apply to branches created
   // or attached after the setting is changed and other objects written
   // after the setting is changed.

   fCompress = settings;
}

//______________________________________________________________________________
void TUDPSocket::NetError(const char *where, Int_t err)
{
   // Print error string depending on error code.

   // Make sure it is in range
   err = (err < kErrError) ? ((err > -1) ? err : 0) : kErrError;

   if (gDebug > 0)
      ::Error(where, "%s", gRootdErrStr[err]);
}

//______________________________________________________________________________
ULong64_t TUDPSocket::GetSocketBytesSent()
{
   // Get total number of bytes sent via all sockets.

   return fgBytesSent;
}

//______________________________________________________________________________
ULong64_t TUDPSocket::GetSocketBytesRecv()
{
   // Get total number of bytes received via all sockets.

   return fgBytesRecv;
}