PDA only receives UDP data when connected to PC; fails wirelessly

[MengHuiHanTang]

I have a UDP sender on PC, a receive program in PDA running Windows Mobile 5.0.

The wired thing is when I connect the PDA with PC through USB cable, receiver program in PDA works fine; but when disconnected, receiver program does not read UDP data any more. 

[Verne_D]

Might you post a list of the values of your controls or a screen shot of the fully configured front panel? It might help illustrate what's going on.

[MengHuiHanTang]

Here is the Sender program, everytime it runs, it broadcasts a 'T' or 'F' to all addresses. 

Here is the receiver program. It is constantly running reading the broadcast message. When PDA is connected to PC, it receives fine; when it disconnects, it does not receive any thing. 

[Verne_D]

Are you getting any errors when this happens or does the program hang? If you are, what errors appear?

[MengHuiHanTang]

Nope, there is no error at all. When PDA is disconnected from PC, the program simply receives nothing without error. I checked the IP settings, it says the submask net is 255.255.255.0, and the assigned IP is 192.168.1.4.

[Verne_D]

Can you verify that the wireless card works when the PDA is not bus powered by the USB through some other means, maybe an internet browser or other equivalent. I'm worried that there are two power modes and one does not keep your network components working properly.

[MengHuiHanTang]

The wireless part physically works fine, because I can communicate with PC through TCP, and can browse internet too. It's just UDP functions that don't receive. 

If the LabVIEW code has nothing wrong, do I need to set up the PDA somehow to receive UDP messages? If TCP works fine, what's the difference between TCP and UDP?

[Verne_D]

I'm not sure. What does the device manufacturer say about UDP communication on the device?

[Verne_D]

Also, TCP and UDP are pretty similar protocols, but there are some details that are not conserved. Google em up and you should find some decent material like this.