如何解压缩通过套接字API发送的数据（结构错误：解压缩需要42个字节的缓冲区）

Question

我正在处理一个家庭作业问题，在该问题中，我设置了一个客户端和服务器程序以模仿DNS请求，从而彼此对话。要发送数据，我正在使用struct.pack和struct.unpack方法。使用sendto（）和recvfrom（）函数打包并发送数据后，我在解压缩数据（4个整数，一个长整数和一个字符串）时遇到了问题。

我尝试了各种格式的字符串，并调用calcsize（）和len（）函数来尝试匹配字节长度要求，但是我仍然遇到此错误（struct.error：unpack需要42个字节的缓冲区）。

服务器端

Sub DeleteMeeting()

Dim i As Long, j As Long
Dim wb              As Workbook
Dim ws              As Worksheet
Dim objOutlook      As Outlook.Application
Dim objNamespace    As Outlook.Namespace
Dim objFolder       As Outlook.MAPIFolder
Dim objAppointment  As Outlook.AppointmentItem

Set objOutlook = Outlook.Application
Set objNamespace = objOutlook.GetNamespace("MAPI")
Set objFolder = objNamespace.GetDefaultFolder(olFolderCalendar)
Set oItems = objFolder.Items
Set wb = ThisWorkbook
Set ws = wb.Worksheets("Licences")


r = ws.Cells(Rows.Count, 1).End(xlUp).Row
For i = 5 To r
    For j = oItems.Count To 1 Step -1

        If Cells(i, 6).Value <> "" And Cells(i, 5) = "Mobile Plant" Then

            Set objAppointment = oItems.Item(j)
            With objAppointment
                If .Subject = "WBC - Send licence - " + ws.Cells(i, 4).Value + " " + ws.Cells(i, 12).Value Then
                    objAppointment.MeetingStatus = olMeetingCanceled
                             .Recipients.Add Sheets("Email List").Range("C3")
                             .Recipients.Add Sheets("Email List").Range("C4")
                             .Recipients.Add Sheets("Email List").Range("C5")
                             .Recipients.Add Sheets("Email List").Range("C6")
                             .Recipients.Add Sheets("Email List").Range("C7")
                             .Recipients.Add Sheets("Email List").Range("C8")
                    objAppointment.Save
                    objAppointment.Send
                End If
            End With
        End If

        If Cells(i, 6).Value <> "" And Cells(i, 5) = "Section 50" Then

            Set objAppointment = oItems.Item(j)
            With objAppointment
                If .Subject = "WBC - Send licence - " + ws.Cells(i, 4).Value + " " + ws.Cells(i, 12).Value Then
                    objAppointment.MeetingStatus = olMeetingCanceled
                             .Recipients.Add Sheets("Email List").Range("C3")
                             .Recipients.Add Sheets("Email List").Range("C4")
                             .Recipients.Add Sheets("Email List").Range("C5")
                             .Recipients.Add Sheets("Email List").Range("C6")
                             .Recipients.Add Sheets("Email List").Range("C7")
                             .Recipients.Add Sheets("Email List").Range("C8")
                    objAppointment.Save
                    objAppointment.Send
                End If
            End With
        End If

        If Cells(i, 6).Value <> "" And Cells(i, 5) = "Section 50 Extension" Then

            Set objAppointment = oItems.Item(j)
            With objAppointment
                If .Subject = "WBC - Send licence - " + ws.Cells(i, 4).Value + " " + ws.Cells(i, 12).Value Then
                    objAppointment.MeetingStatus = olMeetingCanceled
                             .Recipients.Add Sheets("Email List").Range("C3")
                             .Recipients.Add Sheets("Email List").Range("C4")
                             .Recipients.Add Sheets("Email List").Range("C5")
                             .Recipients.Add Sheets("Email List").Range("C6")
                             .Recipients.Add Sheets("Email List").Range("C7")
                             .Recipients.Add Sheets("Email List").Range("C8")
                    objAppointment.Save
                    objAppointment.Send
                End If
            End With
        End If   

        If Cells(i, 6).Value <> "" And Cells(i, 5) = "Non Excavation Permit" Then

            Set objAppointment = oItems.Item(j)
            With objAppointment
                If .Subject = "LBRuT - Send licence - " + ws.Cells(i, 4).Value + " " + ws.Cells(i, 12).Value Then
                    objAppointment.MeetingStatus = olMeetingCanceled
                             .Recipients.Add Sheets("Email List").Range("C3")
                             .Recipients.Add Sheets("Email List").Range("C4")
                             .Recipients.Add Sheets("Email List").Range("C5")
                             .Recipients.Add Sheets("Email List").Range("C6")
                             .Recipients.Add Sheets("Email List").Range("C7")
                             .Recipients.Add Sheets("Email List").Range("C8")
                    objAppointment.Save
                    objAppointment.Send
                End If
            End With
        End If

        If Cells(i, 6).Value <> "" And Cells(i, 5) = "Non Excavation Extension" Then

            Set objAppointment = oItems.Item(j)
            With objAppointment
                If .Subject = "WBC - Send licence - " + ws.Cells(i, 4).Value + " " + ws.Cells(i, 12).Value Then
                    objAppointment.MeetingStatus = olMeetingCanceled
                             .Recipients.Add Sheets("Email List").Range("C3")
                             .Recipients.Add Sheets("Email List").Range("C4")
                             .Recipients.Add Sheets("Email List").Range("C5")
                             .Recipients.Add Sheets("Email List").Range("C6")
                             .Recipients.Add Sheets("Email List").Range("C7")
                             .Recipients.Add Sheets("Email List").Range("C8")
                    objAppointment.Save
                    objAppointment.Send
                End If
            End With
        End If

    Next j
Next i
End Sub

客户端

# Create a UDP socket. Notice the use of SOCK_DGRAM for UDP packets
serverSocket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
# Assign server IP address and port number to socket
serverSocket.bind((serverIP, serverPort))

print("The server is ready to receive on port:  " + str(serverPort))

fileReader = open("dns-master.txt", "r")    # open dns-master.txt
dnsRegistry = []
for line in fileReader:    # read line by line and fill each into a list
    if (line[0] != '#') & (line[0] != "\n"):
        dnsRegistry.append(line.rstrip())
        print(line.rstrip())

# loop forever listening for incoming UDP messages
while True:
    # Receive and print the client data from "data" socket
    data, address = serverSocket.recvfrom(1024)
    print("data length " + str(len(data)))

    unpackedData = unpack('iilii22s', data)
    print("unpacked " + str(unpackedData))

要打包的字段是print(questionString) qs = bytes(questionString, 'utf-8') data = pack('iilii22s', messageType, returnCode, messageIdent, questionLen, answerLen, qs) # pack the data for i in range (0, 3): # send request up to three times # Send data to server print("Sending Request to " + hostIP + ", " + str(port) + ":") print("Message ID: " + str(messageIdent)) print("Question Length: " + str(questionLen) + " bytes") print("Answer Length: " + str(answerLen) + " bytes") print("Question: " + questionString) clientsocket.sendto(data, (hostIP, port)) ，这是我已转换为字节对象的字符串，qs，是介于1到100之间（包括1和100）的随机整数，messageIdent是长度questionLen（在我的情况下为22）中，其余均为0-2之间的整数。我希望服务器程序可以解压缩这些值并将其提取到适当的字段中。当我打印questionString时似乎正在执行此操作，但是我遇到了回溯错误以及我在问题标题中提到的struct.error。

输出：

data

因此，我又如何才能将这些值打包到一个结构中，发送到另一个程序，然后正确地解压缩以便使用这些值？还要注意，当我在服务器端打印The server is ready to receive on port: 9999 host1.student.test A IN 3600 192.168.10.1 host2.student.test A IN 3600 192.168.20.2 host3.student.test A IN 3600 192.168.30.3 host99.student.test A IN 3600 192.168.90.9 host123.student.test A IN 3600 192.168.120.123 Traceback (most recent call last): File "C:/Users/Adam/Documents/NJIT/6. Fall 2019/CS356 - Intro to Computer Networks/DNS-Assignment/server.py", line 32, in <module> unpackedData = unpack('=iilii22s', data) struct.error: unpack requires a buffer of 42 bytes data length 42 unpacked (1, 0, 36, 22, 0, b'host1.student.net A IN') data length 14 时，它被打印两次，并且每次都得到两个不同的值。为什么会这样？