Read NMEA from Server

[schimanski]

Very best thanks, Erel. That what i'am looking for....

[schimanski]

Hello Erel,

thanks for your code. It works very best. But now i have one problem with this code: When the server breaks the connection, my application will stop and I can't do anything. The only thing is to end the application with the task-manager. When there is no data, i can handle the problem, but when the connection breaks, i don't no, how to handle this error.




...schimanski

[Erel]

Can you find the line that gets blocked?

[derez]

I had a similar problem, as mentioned in your first post,that the string does not always start with "$GP..." so I am checking it using strindexof():

instring = Serial.InputString
...
sats() = StrSplit(instring,",")
..
If StrIndexOf (sats(0) , "SA",0) > -1 Then gsa 'for string $GPGSA

the complete application code is here
http://www.basic4ppc.com/forum/showt...=9108#post9108

[schimanski]

Hello Erel, hello Derez!

I can't say, in which line the application locks up. The only thing is to end the app with the task-manager. I think, that the problem is in the sub timer2_tick, because the image4 (it's a little icon 15x15) doesn't change after breaking the server connection.
My english is not so good, so I don't know the function of client.value=server.accept. Is it nessesary to use this line?

[Erel]

server.accept should be called in the server code.
It creates the connection with the client.
The client object that is returned should be used to communicate with the real client.
Can you upload your code file?

[schimanski]

Hello!

I have written a smal testapp to see, where the problem is. When the server sends no data, the application will stop as long, as the server sends data again. When there is data again, the Application runs without any problems. Is there no data, i only can stop the app with the task-manager. Here the code:

Sub App_Start
Form1.Show
timer3.Enabled=true 'timer3=1000 ms'
client.New1
Client.Connect ("87.139.??.???",11112)
filestream.New1(client.GetStream,false)
End Sub

Sub Timer3_Tick
If client.DataAvailable=true Then
filestream.ReadString
label5.Text="data!"
Else
label5.Text="no data!"
End If
End Sub

The server-connection is always available!



Now i have tested more:

The server sends every two seconds a NMEA-protocol. When the timer3 is 2000, the app will run without problems. Is the timer3 500ms, the app will stop, when there is no data. Is the timer3 1000ms, sometimes the app will lockup and another time, the app run without problems, when there is no data. But I need a timerintervall from 500, because when the timer is bigger than 500, i only get old data, not the actually.

[Erel]

Your client code is fine and it should not be blocked.
Can you post your server code?

[schimanski]

Hello Erel!

I can't post the server code, because it's not my application. It is a police-server with an GPS-application, that only provides GPS-data for every officer, who is in duty. Today we have only Notebooks with the same software to get this data. Now, i want' to write a client-application for PDA. I only can say, that the server provides every two seconds a NMEA-String (RMC & GGA) on one port and when there is no data, the server stops providing, but the connection is always available. I don't know the developer of this application, so I can't ask him.
I can' t understand the effects of the different timerintervalls.

[agraham]

Originally Posted by schimanski

I can' t understand the effects of the different timerintervalls.

This is is a wild guess but is it anything to do with the fact that if you wait two seconds then a full message is probably available but polling more often than that it is likely that only part of a message is available. Does your app make the assumption that a full message always arrives as a single read? My experience of the network library is that even small messages can arrive as separate packets so you have to be prepared to reassemble multiple reads into a single message - which is what I believe the GPS library GPSStream method does.