UDP protocol

7 thoughts on “UDP protocol”

1. Hi

   I want to use UDP protocol

   AT#SD = <Conn Id>,<Protocol>, <Remote Port>, <IP address> [, <Closure Type> [, <Local Port>]]

   • Protocol is 0 for TCP and 1 for UDP.

   http://en.wikipedia.org/wiki/User_Datagram_Protocol

   1. When I can get NO CARRIER message?

   2.  Is GE863-GPS generating checksum in UDP packet?

   3. What happend if the checksum in UDP packet received from server will not be valid? 

   I’m using GE863-GPS Firmware 7.03.001.

   1. All the inner UDP work, including checksum, is done by the module stack, you only have to supply the useful packet load. Because UDP is connectionless, the closure is irrelevant, data is sent in separated datagrams; formal socket closure is made with AT#SH.

       

2. OK, another question

    

   Let’s imagine situation:

   1. Module is configured to listen UDP connection via AT#SLUDP

   2. Server sends UDP packet containing data to module.

   3. During transmission UDP packet has been corrupted

   4. Module receives corrupted UDP packet.

   5. What will happen? 

   5.a. Module will send SRING message? How to check if data is corrupted ?

   5.b. UDP packet will be discarded, and module won’t send SRING message?

   5.c. Other event (please describe what will happen) 

3. Well is quite hard to produce such tests, will imply a special written forwarder, and is hard to tell if the packet won’t be discarded by the intermediate links during the transport, I’ll forward to R&D for an answer.

    

   I can assume a wrong packet should silently be discarded, otherwise at least serious security problems can arise.

4. OK I’m waiting for R&D answer.

   If such packet isn’t discarded, I will implement my own chceck sum.

   Thanks for help

   1. The checksum is checked by our stack. If a packet is received with wrong checksum the packet is discarded but the re-transmission is not requested, being an UDP packet.

5. Well all now clear :]

    

   Thanks