Want to learn to be a VB RS232 communication tools, but had been communication on that-CodePudding

 Private Sub Combo1_Click () 'for serial number 
Label6. Caption=Mid (Combo1. Text, 4, 1) 
End Sub 
Private Sub Combo2_click () 'to get the data format 
Label7. Caption=Combo2. Text 
End Sub 
Private Sub Command1_Click () 
Err. Clear 
If Combo1. Text="please select the port number" Or Combo2. Text="please select a data format" Then 
MsgBox "please select the port number and data format" 
ElseIf MSComm1. PortOpen=True Then 
MSComm1. PortOpen=False 
Command1. Caption="open the serial port" 
ElseIf MSComm1. PortOpen=False Then 
'MSComm1. PortOpen=True 
'MsgBox TypeName (CInt (Mid (Combo1. Text, 4, 1))) 

With MSComm1 
CommPort=Val (mids (Combo1. Text, 4, 1)) 
. The Settings=Combo2. Text 
. An InputMode=comInputModeBinary 
. InputLen=0 'each receive bytes 
. SThreshold=8 'set to 0 will not trigger comEvSend 
. RThreshold=1 'receive threshold, when the number of bytes is received & gt;=1, trigger receive events 
InBufferSize=1024 'accept buffer size 
OutBufferSize=1024 'send buffer size 
. InBufferCount=0 
. OutBufferCount=0 
. RTSEnable=True 'receiver function can make 

On the Error Resume Next 
. PortOpen=True 
End With 
Command1. Caption="close serial port" 
The Else 
Label9. Caption="connection is broken!" 

End the If 
If MSComm1. PortOpen=True Then 
Label9. Caption="connection success!" 
Label9. ForeColor=vbGreen 
The Else 
Label9. Caption="connection is broken!" 
Label9. ForeColor=vbRed 
End the If 
'0 means no error occurs, the initial connection normal 
Label10. Caption=Err. Number 
End Sub 

Private Sub Command2_Click () 
Err. Clear 
Label9. Caption="connection is broken!" 
Label9. ForeColor=vbRed 
If MSComm1. PortOpen=True Then MSComm1. PortOpen=False Else MsgBox "not connected, without having to disconnect!" 
End Sub 

Private Sub Command3_Click () 
If MSComm1. PortOpen=True Then 
Dim CMDSTR As String 
Dim sdata As Byte (8) 
Sdata (0)=CByte (& amp; H1) 'CInt (Combo4. Text) 
Sdata (1)=CByte (& amp; H3) 
Sdata (2)=CByte (& amp; H6) 
Sdata (3)=CByte (& amp; H3) 
Sdata (4)=CByte (& amp; H0) 
Sdata (5)=CByte (& amp; H1) 
Sdata (6)=CByte (& amp; H74) 
Sdata (7)=CByte (& amp; H82) 
For I=0 To 7 
If Len (Hex (sdata (I))) for the processing not 0=1 Then 'to fill 
CMDSTR=CMDSTR & amp; "0" & amp; Hex (sdata (I)) 
The Else 
CMDSTR=CMDSTR & amp; Hex (sdata (I)) 
End the If 
Next I 

MSComm1. The Output=CMDSTR 
Label12. Caption=CMDSTR 
Label15. Caption mEvent=MSComm1.Com 
End the If 
End Sub 

Private Sub Command4_Click () 'to close the window 
If MSComm1. PortOpen=True Then MSComm1. PortOpen=False 
Unload Form1 
End Sub 

Private Sub Command5_Click () 
Label11. Caption="" 
Label12. Caption="" 
MSComm1. InBufferCount=0 
MSComm1. OutBufferCount=0 

End Sub 

Private Sub form_load () 
Timer1. Interval=500 '500 ms 
Timer1. Enabled=True 

Dim I, iCounter As Integer 
ICounter=0 
For I=1 To 16 'cycle test serial 
MPort=I 
 MSComm1.ComOn the Error Resume Next 
MSComm1. PortOpen=True 
If Err. Number & lt;> Then 8002 
MSComm1. PortOpen=False 
Combo3. AddItem "COM" & amp; CStr (I), iCounter 
ICounter=iCounter + 1 
End the If 
Next I 
If Combo3. ListCount & gt; 0 Then Combo3. ListIndex=0 

End Sub 
Private Sub MSComm1_OnComm () 
Dim inx () As Byte 
Select Case mEvent MSComm1.Com 
Case comEvReceive 
Label13. Caption="came in?" '... Receive data 
Inx=MSComm1. Input 
'MSComm1. InBufferCount=0 
For k=0 To 7 
TMPSTR=TMPSTR & amp; "/" & amp; Hex (inx (k)) 
Next k 
Label11. Caption=TMPSTR '... Receive data 
End the Select 
End Sub 

Private Sub Timer1_Timer () 'entered here triggered after according to the set time, but need a global variable 
'the Label13. Caption="Interval=" & amp; CStr (ivisibal * 1) 
'If ivisibal Mod 2=0 Then implementation effect 
'the Command1. Visible=True 
'the Label13. Visible=True 
'the Else 
'the Command1. Visible=False 
'the Label13. Visible=False 
'End If 
Ivisibal=ivisibal + 1 

End Sub

Question:
1, whether the connection is successful, whether directly use PortOpen=TRUE? Or how to drop?
2, remove the question 1, is now under the procedures and a connection machine equipment, such as servo drive, even if I send data write death there, as shown above:

 Private Sub Command3_Click () 
If MSComm1. PortOpen=True Then 
Dim CMDSTR As String 
Dim sdata As Byte (8) 
Sdata (0)=CByte (& amp; H1) 'CInt (Combo4. Text) 
Sdata (1)=CByte (& amp; H3) 
Sdata (2)=CByte (& amp; H6) 
Sdata (3)=CByte (& amp; H3) 
Sdata (4)=CByte (& amp; H0) 
Sdata (5)=CByte (& amp; H1) 
Sdata (6)=CByte (& amp; H74) 
Sdata (7)=CByte (& amp; H82) 
For I=0 To 7 
If Len (Hex (sdata (I))) for the processing not 0=1 Then 'to fill 
CMDSTR=CMDSTR & amp; "0" & amp; Hex (sdata (I)) 
The Else 
CMDSTR=CMDSTR & amp; Hex (sdata (I)) 
End the If 
Next I 

MSComm1. The Output=CMDSTR

By displaying the outbuffercount has a value of 0, if there is not data buffer, stop at 0 OMcomm events at the same time, the whole 3 days, is trying not to come out,

question 3: requirements for data types have MSCOMM attributes, such as whether the COMMPORT must be converted to an integer, such as: Cint () (if I use the variable to transfer instead of writing death)

nullnullnullnullnullnullnullnullnullnullnullnullnullnullnullnullnullnullnullnullnullnull