Hi Judith,
John is right. The problem is that when using non-blocking I/O the
splitting send does not work correctly since I don't handle the EWOULDBLOCK
case in TUnixSystem::UnixSend(). The best work around is to make the socket
blocking just before sending a large buffer and unblock it afterwards.
Cheers, Fons.
>
> hi John,
>
> Root takes care of splitting the message into pieces that matches the
> buffersize of the system and sending them (see Fons' email to roottalk).
>
> I suspect (if I didn't do anything wrong), that something goes wrong with
> the synchronizing of these packages if the socket is in non-splitting mode.
>
> cheers,
> Judith
>
> On Wed, 7 Apr 1999, John Zweizig wrote:
>
> > It sounds like your problem is that you don't have a large enough system
> > send buffer. The usual way to fix this is with setsockopt(SO_SNDBUF, nnnn)
> > (nnn is the buffer size to be used), but I don't know how to translate
> > this into root TSockets (I don't see it documented in the online TSocket
> > class description) and you run the risk of getting errors if the buffer
> > hasn't been fully transferred. The easy way around this is to use a
> > blocking socket for your sends. The send() function then makes sure
> > everything works out OK. This should only take a few extra milliseconds
> > while the data are pushed out over the ethernet (or whatever you use) and
> > you won't be able to respond to any further requests during that time anyway.
> > Best regards,
> >
> > John
> >
> > On Wed, 7 Apr 1999, Judith Katzy wrote:
> >
> > >
> > > hi there,
> > >
> > > I'd like to send messages of about 300k in a client server environment
> > > using TSocket and TServerSocket.
> > > Everything works fine as long as I use the blocking mode for
> > > the socket. It also works, if I use the non-blocking mode and just send
> > > small objects (280 bytes).
> > > I get the following error on the server side, when I use the non-blocking
> > > mode with a 300k messages:
> > >
> > > root [1] .x server.C
> > > received mess 'waiting'
> > > SysError in <TUnixSystem::UnixSend>: send (Resource temporarily
> > > unavailable)
> > > Error in <TUnixSystem::SendRaw>: cannot send buffer
> > > server: error occcurred during sending event
> > >
> > > Attached, I send the macros server.C and client.C.
> > >
> > > My suspecion is, that something goes wrong when I send several
> > > packets with TCP/IP in a non-blocking mode, even when the
> > > sending is synchronized.
> > >
> > > thanks for any help,
> > > Judith
> > >
> > > +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> > > macro serroot.C
> > > +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> > > {
> > > // just a large object (buf size about 300k), I take a data event here
> > > TPhEvent *ev = dst->GetNextEvent() ;
> > > TMessage smess(kMESS_OBJECT);
> > > smess->WriteObject(ev);
> > > TServerSocket *ss = new TServerSocket(9091, kTRUE);
> > > TSocket *s0 = ss->Accept();
> > > s0->SetOption(kNoBlock,1);
> > > Int_t fSend,idx;
> > >
> > > Char_t str[32];
> > > Int_t fRecv, fSend;
> > >
> > > while (1)
> > > {
> > > fRecv = s0->Recv(str,32);
> > > if(fRecv != -4)
> > > {
> > > // client request new event
> > > idx = !strcmp(str, "waiting") ? 0 : 1;
> > > if(idx == 0)
> > > {
> > > printf("received mess '%s'\n",str);
> > > //***fSend = s0->Send("xxx");
> > > UInt_t what = smess->What();
> > > // synchronize sending
> > > smess->SetWhat(what || kMESS_ACK);
> > > fSend = s0->Send(smess);
> > > if(fSend==-1)
> > > printf("server: error occcurred during sending event\n");
> > > }
> > > }
> > > }
> > > s0->Close();
> > > ss->Close();
> > > }
> > >
> > > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> > > macro client.C
> > > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> > >
> > > {
> > > TSocket *csock = new TSocket("judithpc.phy.uic.edu", 9091);
> > > csock->Send("waiting");
> > > TMessage *mess;
> > > Int_t fRecv;
> > > Int_t idx;
> > > Char_t cstr[256];
> > > while (1) {
> > > //** fRecv = csock->Recv(cstr,32);
> > > fRecv = csock->Recv(mess);
> > > if(fRecv!=-4){
> > > if(fRecv<0)
> > > {
> > > printf("error message received, error code %d -return\n ",fRecv);
> > > return;
> > > }
> > > //**printf("received %s\n",cstr);
> > > TPhEvent *event = (TPhEvent *)mess->ReadObject(mess->GetClass());
> > > printf("received %d, event %d\n",mess->What(),event->GetNEvent());
> > > csock->Send("waiting");
> > > delete mess;
> > > }
> > > }
> > > csock->Close();
> > > }
> > >
> > >
> > >
> > >
> > >
> >
--
Org: CERN, European Laboratory for Particle Physics.
Mail: 1211 Geneve 23, Switzerland
E-Mail: Fons.Rademakers@cern.ch Phone: +41 22 7679248
WWW: http://root.cern.ch/~rdm/ Fax: +41 22 7677910
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