Agilent Technologies 4294A Service Manual download pdf (Page 182)

182 Chapter 12

Using LAN

Controlling the Agilent 4294A

MsgBox ("ERROR: socket = " + Str$(socketId)) '...................(2)

OpenSocket = COMMAND_ERROR '

Exit Function '

End If '

'Open a connection to a server

I_SocketAddress.sin_family = AF_INET '

I_SocketAddress.sin_port = htons(PortNumber) '...................(3)

I_SocketAddress.sin_addr = ipAddress '

I_SocketAddress.sin_zero = String$(8, 0) '

x = connect(socketId, I_SocketAddress, Len(I_SocketAddress)) '

If socketId = SOCKET_ERROR Then '

MsgBox ("ERROR: connect = " + Str$(x)) '..........(4)

OpenSocket = COMMAND_ERROR '

Exit Function '

End If '

OpenSocket = socketId

End Function

Communication

The subprogram corresponding to transmit in communication is SendCommand (Example 12-4).

SendCommand uses the send function of WinSock API to transmit a message (GPIB command)

specified by command, an input parameter, to the

4294A. Parameters for the send function are

Socket Descriptor (input), Transmit Message (input). Message Length (input) and Flag (input).

Example 12-4 SendCommand

Function SendCommand(ByVal command As String) As Integer

Dim strSend As String

strSend = command + vbCrLf

count = send(socketId, ByVal strSend, Len(strSend), 0)

If count = SOCKET_ERROR Then

MsgBox ("ERROR: send = " + Str$(count))

SendCommand = COMMAND_ERROR

Exit Function

End If

SendCommand = NO_ERROR

End Function

Subprograms corresponding to receive in communication are RecvAscii (Example 12-5) and others.

RecvAscii receives a message in the ASCII format, and store it dataBuf, an output parameter. The

maximum length of a message it receives is specified through maxLength, an input parameter. Below

are described steps of RecvAscii:

In (1), the recv function of WinSock API is used to receive a message (response to Query, an GPIB

command) on a character-by-character basis. If an error occurs during this operation, the function

outputs a message and returns processing to the main program. Parameters for the recv function are

Socket Descriptor (input), Receipt Message (output), Message Length (input), and Flag (input).

In (2), whether a received character is LF (ASCII code No.: 10) is determined, and if LF, NULL

(ASCII code No.: 0) is added to the tail of the character string dataBuf, receipt is ended, and

processing returns to the main program.

In (3), the number of characters read immediately before is added to the count for checking the

number of received characters, and characters read are added to the tail of the character string

dataBuf.

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Agilent Technologies 4294A Service Manual Page 182

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