How to read incoming tcp data packet - string not empty but no data ?
Posted
#1
(In Topic #741)
Trainee
wrote a small program to communicate with a android tablet. The program consist of label,textarea and buttons,serversocket. The tablet has a small porgram written in B4A which send a code over wifi to the ethernet connected pc where the gambas program runs.
I have a connection as gambas sees the ip addres and the selected port which is shown in the textarea. Connect to : <ipaddres> port:<port where serversocket listens>
The progam is inspired from the blog Capain Bodgit,( thanks mr SteveDee)
I have the connection and port listening though i cannot read the message send from the tablet( confirmed by the B4A packet send). the message consist of a single coordinate like "01" . In a terminal tcdpdump is see a packet with lenght 6.
In the gambas program when i look at the length of the strmsg from the Socket_read() sub from mysocket it is also 6 but i don't find a way to show it here in message.
The tables send the message string as bytes i suppose. Do i have a data conversion problem or has it a diffrent cause.
Thanks for your help.
Gambas class file
Code
' Gambas class file
Public Sub Form_Open()
ServerSocket1.port = 12345
ServerSocket1.type = Net.Internet
End
Public Sub Form_Close()
If ServerSocket1.Status Then
ServerSocket1.Close
Endif
End
Public Sub btlisten_Click()
ServerSocket1.Listen(1)
If ServerSocket1.status = Net.active Then
btlisten.Enabled = False
lbIpstatus.text = "Connected - Listen to port: " & ServerSocket1.Port
Endif
End
Public Sub btQuit_Click()
If ServerSocket1.Status Then
ServerSocket1.close
Endif
Quit
End
Public Sub btverbose_Click()
Dim shellvar As String
taInfo.text = gb.crlf & ServerSocket1.status & gb.crlf & "------------------------------------------------------------------" & gb.CrLf
Shell "netstat -at | grep 'LISTEN'" To shellvar
taInfo.text &= shellvar
End
Public Sub ServerSocket1_Connection(RemoteHostIP As String)
Dim strmsg As String
Dim mysocket As Socket
If ServerSocket1.Status > Net.Inactive Then
mysocket = ServerSocket1.Accept()
mysocket.Blocking = False
If mysocket.Status = Net.Connected Then
taInfo.text &= gb.crlf & "Connected: " & mysocket.RemoteHost & " Port:" & mysocket.RemotePort & gb.CrLf
Else
taInfo.text &= gb.crlf & "SocketStatus: " & mysocket.Status & " not Net.connected " & gb.CrLf
Endif
Endif
End
Public Sub Socket_read()
Dim strMsg As String
Dim convmsg As String
If Last.status <> Net.Connected Then
taInfo.Text &= "no incoming message."
Return
Else
Read #Last, strMsg, Lof(Last)
If strmsg = "" Then
strmsg = "empty"
Endif
Message("Lenght: " & String.Len(strmsg) & gb.CRLF & " strmsg: " & Str$(strmsg))
Endif
End
Public Sub Socket_closed()
taInfo.text &= gb.crlf & "Connection with socket closed"
End
Public Sub ServerSocket1_Error()
Message.Error("Unable to bind socket")
End
Public Sub btCloseServer_Click()
If ServerSocket1.Status Then
ServerSocket1.Close
btlisten.Enabled = True
lbIpstatus.text = "Port closed - Disconnected"
Endif
End
Posted
Guru
You seem to have a mix of Socket_EventName() and ServerSocket1_EventName() methods.
The object you added to the Form Designer called ServerSocket1 will use ServerSocket1_EventName() for all events
Socket_Closed() will not trigger either for ServerSocket1
Posted
Guru
Message("Lenght: " & String.Len(strmsg) & gb.LF & " strmsg: " & Quote(strmsg))
Also i'd only use gb.Lf not gb.CrLf in a message
A message box will turn a gb.LF \n into <br> but the CR may have unwanted results.
Str() is for converting a Value to a string and strmsg is probably already a String the tcp message is probably text so Str() is not wanted.
Posted
Trainee
Re:Solved- How to read incoming tcp data packet - string not empty but no data ?
Dear Mr Brucesteers,thanks for the swift replys. The code provided by Mr SteveDee on his Captain Bodgit website is correct.
Tried to change the Socket_read sub to ServerSocket1_read but did not work.
The Socket_read is used and gives me the messagbox information as test.
Thanks for the 'Quote' tip , did not know this function.
Data from android tablet send : "01"
Data received in Quote(strmsg) = "\x00\x00\x00\x0201"
Data from android tablet send : "12"
Data received in Quote(strmsg) = "\x00\x00\x00\x0212"
I do not know what I see ,how to understand what these "\x00\x00\x00\x02" signs are.
But as suggested what to trim solved it with a simple trim function
Trim(strmsg) = "01"
Trim(strmsg)= "12"
Runs now fine and data is presented in the textarea object.
Thanks Mr BruceSteers
Code
Public Sub Socket_Read()
Dim strMsg As String
If Last.Status <> Net.Connected Then
TextArea1.Text &= "No incoming message: " & Trim(strMsg) & gb.Lf
Return
Else
Read #Last, strMsg, Lof(Last)
TextArea1.Text &= "Incoming message: " & Trim(strMsg) & gb.Lf
Endif
End
Posted
Guru
dinge said
Dear Mr Brucesteers,
thanks for the swift replys. The code provided by Mr SteveDee on his Captain Bodgit website is correct.
Tried to change the Socket_read sub to ServerSocket1_read but did not work.
The Socket_read is used and gives me the messagbox information as test.
Thanks for the 'Quote' tip , did not know this function.
Data from android tablet send : "01"
Data received in Quote(strmsg) = "\x00\x00\x00\x0201"
Data from android tablet send : "12"
Data received in Quote(strmsg) = "\x00\x00\x00\x0212"
I do not know what I see ,how to understand what these "\x00\x00\x00\x02" signs are.
But as suggested what to trim solved it with a simple trim function
Trim(strmsg) = "01"
Trim(strmsg)= "12"
Runs now fine and data is presented in the textarea object.
Thanks Mr BruceSteersCode
Public Sub Socket_Read()
Dim strMsg As String
If Last.Status <> Net.Connected Then
TextArea1.Text &= "No incoming message: " & Trim(strMsg) & gb.Lf
Return
Else
Read #Last, strMsg, Lof(Last)
TextArea1.Text &= "Incoming message: " & Trim(strMsg) & gb.Lf
Endif
End
cool glad i got it right in amongst all that getting it wrong i did lol
Nice that Trim() works
Other option (if trim did not work) would be..
If InStr(strMsg, "\x02") then strMsg = Split(strMsg, "\x02")[1] ' Get the text to the right of the \x02
Quote() can be very handy in figuring out what's happening.
Here's another tip
Using TextArea1.Text &= "more text" will cause textarea to jump around a bit (it basically erases the controls entire text then re-writes it all each time, it's just a bit ugly and noticeable on slow machines)
Using TextArea1.Insert("more text" & gb.Lf) does a nice clean append to the textarea
Posted
Regular
dinge said
…Data from android tablet send : "01"
Data received in Quote(strmsg) = "\x00\x00\x00\x0201"
Data from android tablet send : "12"
Data received in Quote(strmsg) = "\x00\x00\x00\x0212"
I do not know what I see ,how to understand what these "\x00\x00\x00\x02" signs are…
Hi dinge, I've just returned from a short holiday, so only just read your post.
Your problem is that the B4A program is not formatting the transmitted data in the format expected by your Gambas code.
You might find it interesting to make a Gambas Client Socket to run alongside your Gambas Server Socket and do a few simple tests. If your Client sends text like this:-
…the Server Socket will receive the text correctly.
But if you send a 4 byte integer like this:-
…the server will receive: \x00\x00\x00\x0B
And if you send text like this:-
…the Server will show: \x0211
which means; Length = 2, Text = 11
So I think you should check the B4A documentation and see if there is a format you can use that suits Gambas. (i.e. It looks like B4A is sending Integer data, but you are expecting Strings.)
Also, you can change the Gambas Server Read to suit other data types. For example:-
…could be replaced with something like this:-
I hope this helps.
Posted
Trainee
thanks for your information. Indeed B4A sends the strings as raw data = bytes packets. As you suggested I looked into the B4A code and there is a way to send the string data otherwise. Will have to continue to work on that.
Apologize for the late reply , I work on this only in freetime.
Thanks again and greetings
Dusselier Francis
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