利用Telnet服务器进行控制
概述
这部分说明在Windows环境中如何使用WinSock API控制E5071C。
在Excel VBA中的样本程序
在Microsoft Excel中打开ctrl_lan.xls，显示屏幕如下图所示。
参考以下说明,了解如何使用ctrl_lan.xls中的每一项。
在“Winsock版本”右边单元格输入WinSock API的版本号。版本号是主版本号乘以256，再加上次版本号。例如，您的Winsock API版本是1.1，版本号可按如下方法得出：在“IP地址”右侧单元格输入E5071C的IP地址。如果这两个区域的值不正确，VBA宏就不能正常运行。
在第2部分，设置扫描范围（开始点和停止点）与测量点数。点击设置，执行由设置表指定的设置操作，同时点击标有“询问”的按钮，恢复E5071C的当前设置。
第3部分只设置触发模式。
第4部分设置通道1中迹线1的测量参数和数据格式。点击设置，执行由设置表指定的设置操作，同时点击标有“询问”的按钮，恢复E5071C的当前设置。
在第5部分，点击自动调整，自动调整通道1中迹线1。
点击第6部分中的读出迹线，恢复通道1中迹线1的格式化数据。数据以列表和图形格式表示。
点击预置，执行预置操作。
VBA宏中的操作说明
这部分描述VBA宏的操作，重点放在与WinSock API控制相关的部分。
为了使用WinSock API，您必须通过WinSock API的定义文件声明函数并定义变量，这在WinSock API的定义文件中有详细说明。
WinSock API定义文件
'This is the Winsock API definition file for Visual Basic
'Setup the variable type 'hostent' for the WSAStartup command
Type Hostent
h_name As Long
h_aliases As Long
h_addrtype As String * 2
h_length As String * 2
h_addr_list As Long
End Type
Public Const SZHOSTENT = 16
'Set the Internet address type to a long integer (32-bit)
Type in_addr
s_addr As Long
End Type
'A note to those familiar with the C header file for Winsock
'Visual Basic does not permit a user-defined variable type
'to be used as a return structure. In the case of the
'variable definition below, sin_addr must
'be declared as a long integer rather than the user-defined
'variable type of in_addr.
Type sockaddr_in
sin_family As Integer
sin_port As Integer
sin_addr As Long
sin_zero As String * 8
End Type
Public Const WSADESCRIPTION_LEN = 256
Public Const WSASYS_STATUS_LEN = 128
Public Const WSA_DescriptionSize = WSADESCRIPTION_LEN + 1
Public Const WSA_SysStatusSize = WSASYS_STATUS_LEN + 1
'Setup the structure for the information returned from
'the WSAStartup() function.
Type WSAData
wVersion As Integer
wHighVersion As Integer
szDescription As String * WSA_DescriptionSize
szSystemStatus As String * WSA_SysStatusSize
iMaxSockets As Integer
iMaxUdpDg As Integer
lpVendorInfo As String * 200
End Type
'Define socket return codes
Public Const INVALID_SOCKET = &HFFFF
Public Const SOCKET_ERROR = -1
'Define socket types
Public Const SOCK_STREAM = 1 'Stream socket
Public Const SOCK_DGRAM = 2 'Datagram socket
Public Const SOCK_RAW = 3 'Raw data socket
Public Const SOCK_RDM = 4 'Reliable Delivery socket
Public Const SOCK_SEQPACKET = 5 'Sequenced Packet socket
'Define address families
Public Const AF_UNSPEC = 0 'unspecified
Public Const AF_UNIX = 1 'local to host (pipes, portals)
Public Const AF_INET = 2 'internetwork: UDP, TCP, etc.
Public Const AF_IMPLINK = 3 'arpanet imp addresses
Public Const AF_PUP = 4 'pup protocols: e.g. BSP
Public Const AF_CHAOS = 5 'mit CHAOS protocols
Public Const AF_NS = 6 'XEROX NS protocols
Public Const AF_ISO = 7 'ISO protocols
Public Const AF_OSI = AF_ISO 'OSI is ISO
Public Const AF_ECMA = 8 'european computer manufacturers
Public Const AF_DATAKIT = 9 'datakit protocols
Public Const AF_CCITT = 10 'CCITT protocols, X.25 etc
Public Const AF_SNA = 11 'IBM SNA
Public Const AF_DECnet = 12 'DECnet
Public Const AF_DLI = 13 'Direct data link interface
Public Const AF_LAT = 14 'LAT
Public Const AF_HYLINK = 15 'NSC Hyperchannel
Public Const AF_APPLETALK = 16 'AppleTalk
Public Const AF_NETBIOS = 17 'NetBios-style addresses
Public Const AF_MAX = 18 'Maximum # of address families
'Setup sockaddr data type to store Internet addresses
Type sockaddr
sa_family As Integer
sa_data As String * 14
End Type
Public Const SADDRLEN = 16
'Declare Socket functions
Public Declare Function closesocket Lib "wsock32.dll" (ByVal s As Long) As Long
Public Declare Function connect Lib "wsock32.dll" (ByVal s As Long, addr As sockaddr_in, ByVal namelen As Long) As Long
Public Declare Function htons Lib "wsock32.dll" (ByVal hostshort As Long) As Integer
Public Declare Function inet_addr Lib "wsock32.dll" (ByVal cp As String) As Long
Public Declare Function recv Lib "wsock32.dll" (ByVal s As Long, ByVal buf As Any, ByVal buflen As Long, ByVal flags As Long) As Long
Public Declare Function recvB Lib "wsock32.dll" Alias "recv" (ByVal s As Long, buf As Any, ByVal buflen As Long, ByVal flags As Long) As Long
Public Declare Function send Lib "wsock32.dll" (ByVal s As Long, buf As Any, ByVal buflen As Long, ByVal flags As Long) As Long
Public Declare Function socket Lib "wsock32.dll" (ByVal af As Long, ByVal socktype As Long, ByVal protocol As Long) As Long
Public Declare Function WSAStartup Lib "wsock32.dll" (ByVal wVersionRequired As Long, lpWSAData As WSAData) As Long
Public Declare Function WSACleanup Lib "wsock32.dll" () As Long
Public Declare Function WSAUnhookBlockingHook Lib "wsock32.dll" () As Long
Public Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (hpvDest As Any, hpvSource As Any, ByVal cbCopy As Long)
WinSock API的基本控制流程如下图所示：
WinSock API控制流程
下面说明WinSock API控制流程的各个步骤。
启动
与启动相关的程序是StartIt。StartIt通过WSAStartup启动并初始化WinSock API，其版本在ctrl_ lan.xls的第1部分进行了说明。人们通常在初始化WinSock时使用WSAStartup函数。这个函数用版本号（输入）与启动信息（输出）作为参数。
StartIt
Sub StartIt()
Dim StartUpInfo As WSAData
'Version 1.1 (1*256 + 1) = 257
'version 2.0 (2*256 + 0) = 512
'Get WinSock version
Sheets("Sheet1").Select
Range("C2").Select
version = ActiveCell.FormulaR1C1
'Initialize Winsock DLL
x = WSAStartup(version, StartUpInfo)
End Sub
Socket Creation与Connection
SocketCreation与Connection的程序是OpenSocket。OpenSocket连接与输入参数主机名指定IP地址相关的仪器。它使用由输入参数指定的端口socket。下面说明OpenSocket各个部分的功能。
在（1）中，WinSock API的inet_aadr函数将由“.”分开的IP地址转换成Internet地址。
在（2）中，WinSock API的socket函数创建一个新socket，并获得socket描述符。如果发生了错误，该控制会向主程序返回消息。Socket函数用地址族（输入）、socket type（输入）和协议号（输入）作为其参数。
在（3）中，socket address是经过指定的。注意，用于指定端口号的htons是WinSock API的一个函数。这个函数将Windows字节顺序（小头）的2字节整数转换成网络字节顺序（大头）。
在（4）中，使用WinSock API的connect函数建立与E5071C的连接。如果发生了错误，该控制会向主程序返回消息。connect函数用socket描述符（输入）、socket地址（输入）和socket地址的大小（输入）作为其参数。
OpenSocket
Function OpenSocket(ByVal Hostname As String, ByVal PortNumber As Intege r) As Integer
Dim I_SocketAddress As sockaddr_in
Dim ipAddress As Long
ipAddress = inet_addr(Hostname) '...........(1)
'Create a new socket
socketId = socket(AF_INET, SOCK_STREAM, 0) '
If socketId = SOCKET_ERROR Then '
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$(x)) '..(4)
OpenSocket = COMMAND_ERROR '
Exit Function '
End If '
OpenSocket = socketId
End Function
传送
与传送相关的程序是SendCommand。SendCommand把输入参数“命令”指定的消息（SCPI命令）传送到使用WinSock API send函数的E5071C。send函数用socket描述符（输入）、待传送的消息（输入）、消息的长度（输入）和标记（输入）作为参数。
SendCommand
Function SendCommand(ByVal command As String) As Integer
Dim strSend As String
strSend = command + vbCrLf
count = send(socketId, ByVal strSend, Len(strSend), 0)
If count = SOCKET_ERROR Then
MsgBox ("ERROR: send = " + Str$(count))
SendCommand = COMMAND_ERROR
Exit Function
End If
SendCommand = NO_ERROR
End Function
与传送的接收部分相关的程序是RecvAscii与其他函数。RecvAscii接收ASCII格式的消息，并将其储存到数据缓冲区输出参数中。消息的最大长度由最大长度输入参数指定。下面说明RecvAscii各个部分的功能。
在（1）中，使用WinSock API的recv函数接收作为系列字符的E5071C的消息（SCPI命令询问的响应）。如果发生错误，该控制会向主程序返回消息。recv函数用socket描述符（输入）、待接收的消息（输入）、消息长度（输入）和标记（输入）作为其参数。
在（2）中，这取决于每个接收的字符是否为换行字符（ASCII码：10）。当接收的字符为换行符时，在数据缓冲区字符串的末端添加NULL（ASCII码：0），接收被中断，并控制返回到主程序。
在（3）中，把最后读出的字符数添加到计数值，以检查接收到的字符数，并把字符附加到数据缓冲区字符串的末端。
Function RecvAscii(dataBuf As String, ByVal maxLength As Integer) As Integer
Dim c As String * 1
Dim length As Integer
dataBuf = ""
While length < maxLength
DoEvents
count = recv(socketId, c, 1, 0) '
If count < 1 Then '
RecvAscii = RECV_ERROR '............(1)
dataBuf = Chr$(0) '
Exit Function '
End If '
If c = Chr$(10) Then '
dataBuf = dataBuf + Chr$(0) '............(2)
RecvAscii = NO_ERROR '
Exit Function '
End If '
length = length + count '............(3)
dataBuf = dataBuf + c '
Wend
RecvAscii = RECV_ERROR
End Function
断开
与断开相关的程序是CloseConnection。CloseConnection断开传送并使用WinSock API的closesocket函数移动socket。Closesocket函数用socket描述符（输入）作为其参数。
Sub CloseConnection()
x = closesocket(socketId)
If x = SOCKET_ERROR Then
MsgBox ("ERROR: closesocket = " + Str$(x))
Exit Sub
End If
End Sub
End
与结束相关的程序是EndIt。EndIt使用WinSock API的WSACleanup函数断开WinSock API。中断WinSock时，通常应使用函数WSACleanup。
Sub EndIt()
'Shutdown Winsock DLL
x = WSACleanup()
End Sub
控制示例
按顺序执行上述程序就可以控制E5071C，按使用WinSock API的控制流程进行控制。在自动调整中所描述的自动调整程序（点击自动调整按钮时就可以执行的程序）可以证明这一点。
自动调整
Sub autoscale()
'
' auto scaling
'
Call StartIt
Call get_hostname
x = OpenSocket(Hostname$, ScpiPort)
x = SendCommand(":DISP:WIND1:TRAC1:Y:AUTO")
Call CloseConnection
Call EndIt
End Sub
当您通过连接并断开每个命令的socket执行多个命令时，执行顺序可能会发生改变。