UDP Rx poblem

8 thoughts on “UDP Rx poblem

  1. Im having a problem getting the module to work in UDP mode Im using the #SD command to create the connection. I am able to send data from the unit to our server however it never sees the data sent from the server

    Im using

    but when I get the status of the connection it shows that the local post is 18183 in this case it changes ever time the connection is created but I have explicitly set the local port as 5001 in the dial command.


    #SS: 1,2,,18183,,5001
    #SS: 2,0
    #SS: 3,0
    #SS: 4,0
    #SS: 5,0
    #SS: 6,0

    Am I missing a command that will allow the unit to receive data?
    I have added the server IP to the internal  firewall.
    One thing to note is that if our server Broadcasts the data the unit sees it so I know the unit is capable of receiving data just not targeted data.

      1. Hi Richard, your modules have public IP addresses or are in a network provided VPN?

        They are using a public APN

  2. It was a problem in older firmware versions, setting the port with <connMode> 0 or 1, the udp local port is not set and a random, larger port number is used. If <connMode> is not set, the UDP local port is used. Is fixed since 7.03.xx1, please upgrade your modules.


    1. I have updated the module to 7.03.401 and the response from the #ss command now indicates that the module is using the requested port however I’m still unable to send data to the module.


      Again If I broadcast the data from my server the module does see the data but targeting the data to the IP of the module (as reported by the incoming packet received by the server) the module doesn’t appear to see the data. 

      1. So is a private network space , how your returning messages are supposed to traverse the network gateway back to your module, being an UDP connectionless link in client mode?


        Maybe the following quotes can help?

        … packets that flow from a client to a server and those that flow in the
        opposite direction are, in some way, unrelated. I mean: in a TCP
        connection a channel is established and a client and a server
        communicate over that channel; in UDP a client sends a “message” to a
        server and closes, and the server sends a “message” to a client and
        closes: no complicated checks, no connections.


        UDP is inherently oneway, so there can be no direct response to a UDP
        message, such as return values for a remote operation call.


        1. The modules internal IP is but when the server receives the packet we see the modules external IP which is the address we respond to I was under the impression that the translation from the external IP to the internal IP is done by the network provider as it is the one that assigned the external IP to the module and I believe that mapping would remain for several minutes.

          is this not the case ?

          1. No, that is gateway’s address, many devices use it to go out, it cannot be assigned to your single device.

            There are many texts describing Internet and private networks connectivity, gateways, routers, firewalls, forwarding etc., these apply also to GPRS and 3G networks.