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Reference Guide
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)
// 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)
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 mess(kMESS_OBJECT | kMESS_ACK);
// Fill histogram randomly
Float_t px, py;
const int kUPDATE = 1000;
for (int i = 0; i < 25000; i++) {
if (idx == 0)
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);
// Close the socket
Definition: MessageTypes.h:35
const Bool_t kFALSE
Definition: RtypesCore.h:88
bool Bool_t
Definition: RtypesCore.h:59
float Float_t
Definition: RtypesCore.h:53
R__EXTERN TBenchmark * gBenchmark
Definition: TBenchmark.h:59
R__EXTERN TRandom * gRandom
Definition: TRandom.h:62
virtual void SetFillColor(Color_t fcolor)
Set the fill area color.
Definition: TAttFill.h:37
virtual void Start(const char *name)
Starts Benchmark with the specified name.
Definition: TBenchmark.cxx:174
virtual void Show(const char *name)
Stops Benchmark name and Prints results.
Definition: TBenchmark.cxx:157
1-D histogram with a float per channel (see TH1 documentation)}
Definition: TH1.h:571
The TH1 histogram class.
Definition: TH1.h:56
virtual Int_t Fill(Double_t x)
Increment bin with abscissa X by 1.
Definition: TH1.cxx:3275
2-D histogram with a float per channel (see TH1 documentation)}
Definition: TH2.h:251
static void EnableSchemaEvolutionForAll(Bool_t enable=kTRUE)
Static function enabling or disabling the automatic schema evolution.
Definition: TMessage.cxx:116
virtual void SetSeed(ULong_t seed=0)
Set the random generator seed.
Definition: TRandom.cxx:597
virtual void Rannor(Float_t &a, Float_t &b)
Return 2 numbers distributed following a gaussian with mean=0 and sigma=1.
Definition: TRandom.cxx:489
void SetCompressionLevel(Int_t level=ROOT::RCompressionSetting::ELevel::kUseMin)
See comments for function SetCompressionSettings.
Definition: TSocket.cxx:1058
virtual Int_t Recv(TMessage *&mess)
Receive a TMessage object.
Definition: TSocket.cxx:816
virtual void Close(Option_t *opt="")
Close the socket.
Definition: TSocket.cxx:388
virtual Int_t Send(const TMessage &mess)
Send a TMessage object.
Definition: TSocket.cxx:521
Fons Rademakers

Definition in file hclient.C.