Applied-motion SV7-Q-EE Manual de usuario descargar pdf (Pagina 18)

6/26/2010

920‐0032a3eSCLCommunicationReferenceManual Page18

Byte[] SCLstring = new Byte[receiveBytes.Length - 2];

// remove opcode

System.Array.Copy(receiveBytes, 2, SCLstring, 0, SCLstring.Length);

receiveString = Encoding.ASCII.GetString(SCLstring);

AddToHistory(receiveString);

}

else if (opcode == 99) // ping response

{

MessageBox.Show("Ping!", "eSCL Utility", MessageBoxButtons.OK,

MessageBoxIcon.Information);

}

Thecallbackfunctionwill notbecalledunlessitis“registered”withtheUdpClientobjectusingthe

BeginReceivemethod,asshownbelow.StartRecvCallbackcanbecalledfromtheFormLoadevent.Itmust

alsobere‐registeredeachtimeitiscalled(thisistopreventrecursion),whichismosteasilya ccomplishedby

makingacalltoStartRecvCallbackeachtimeyousendapacket.

private void StartRecvCallback()

{

UdpState s = new UdpState();

s.e = new IPEndPoint(IPAddress.Any, 0);

s.u = udpClient;

udpClient.BeginReceive(new AsyncCallback(ReceiveCallback), s);

}

ThisexamplerequiresthatyoudeclareaclasscalledUdpStateasdescribedbelow.

class UdpState

{

public UdpClient u;

public IPEndPoint e;

}

Asifthiseventdriventechniquewasn’tquirky enough,italsocreatesathreadingerrorunlessthefollowing

statementinincludedintheformloadevent:

CheckForIllegalCrossThreadCalls = false; // this must be so for callbacks which

operate in a different thread



AppendixC:ExampleTCPProgram

Allexampleprogramsareavailablefordownloadatwww.applied‐

motion.com/ampinfo/software/samplecode/.Youshouldstillreadthissectionsothatyouunderstandthekey

elementsofthecodeandwhattradeoffsyoumayencounter.

VisualBasic6

EventhoughVB6isanolderlanguage,itsrefreshingsimplicitymakesitacompellingchoiceforquickly

developinganEthernetapplication.

TocommunicateoverEthernetTCPfromVB6,you’llneedtheWinsockcontrol(MSWINSCK.OCX),whichis

includedintheProfessionalandEnterpriseeditionsofthelanguage.ToconfigureaninstanceofWinsock,you

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