hclient.C File Reference

Detailed Description

Client program which creates and fills a histogram.

Every 1000 fills the histogram is send to the server which displays the histogram.

To run this demo do the following:

• Open three windows
• Start ROOT in all three windows
• Execute in the first window: .x hserv.C (or hserv2.C)
• Execute in the second and third windows: .x hclient.C If you want to run the hserv.C on a different host, just change "localhost" in the TSocket ctor below to the desired hostname.

The script argument "evol" can be used when using a modified version of the script where the clients and server are on systems with different versions of ROOT. When evol is set to kTRUE the socket will support automatic schema evolution between the client and the server.

void hclient(Bool_t evol=kFALSE)
{
   gBenchmark->Start("hclient");

   // Open connection to server
   TSocket *sock = new TSocket("localhost", 9090);

   // Wait till we get the start message
   char str[32];
   sock->Recv(str, 32);

   // server tells us who we are
   int idx = !strcmp(str, "go 0") ? 0 : 1;

   Float_t messlen  = 0;
   Float_t cmesslen = 0;
   if (idx == 1)
      sock->SetCompressionLevel(1);

   TH1 *hpx;
   if (idx == 0) {
      // Create the histogram
      hpx = new TH1F("hpx","This is the px distribution",100,-4,4);
      hpx->SetFillColor(48);  // set nice fill-color
   } else {
      hpx = new TH2F("hpxpy","py vs px",40,-4,4,40,-4,4);
   }

   TMessage::EnableSchemaEvolutionForAll(evol);
   TMessage mess(kMESS_OBJECT);
   //TMessage mess(kMESS_OBJECT | kMESS_ACK);

   // Fill histogram randomly
   gRandom->SetSeed();
   Float_t px, py;
   const int kUPDATE = 1000;
   for (int i = 0; i < 25000; i++) {
      gRandom->Rannor(px,py);
      if (idx == 0)
         hpx->Fill(px);
      else
         hpx->Fill(px,py);
      if (i && (i%kUPDATE) == 0) {
         mess.Reset();              // re-use TMessage object
         mess.WriteObject(hpx);     // write object in message buffer
         sock->Send(mess);          // send message
         messlen  += mess.Length();
         cmesslen += mess.CompLength();
      }
   }
   sock->Send("Finished");          // tell server we are finished

   if (cmesslen > 0)
      printf("Average compression ratio: %g\n", messlen/cmesslen);

   gBenchmark->Show("hclient");

   // Close the socket
   sock->Close();
}

Author

Fons Rademakers

Definition in file hclient.C.