[lwip-users] ICMP port unreachable when using netconn UDP

[Ben Bobbitt]

I’m running out of ideas for debugging UDP receive under lwip.  

 

I’ve modified an existing app ( for the EVK1100 Atmel ) where I am changing a module from using TCP to using UDP.   This should be trivial, but something just isn’t working

 

All I have done is to make the UDP related changes to the lwipopts.h file, and then in the module that was previously a webserver example:  

 

pxHTTPListener = netconn_new( NETCONN_UDP );

addr.addr = htonl(0xc0a80002);  // my local ip 192.168.0.2

netconn_bind(pxHTTPListener, &addr, webHttpPort );

addr.addr = htonl(0xc0a80065);  // ip of the remote system

netconn_connect(pxHTTPListener,&addr,webHttpPort);

nbRecv = netconn_recv(pxHTTPListener);

while (1)

  vTaskDelay( webSHORT_DELAY );

 

 

When sending a UDP packet from a remote system, the ARP exchange works and resolves to the correct IP, but then the Atmel system returns an ICMP port unreachable response.   The target port is the defined webHttpPort (yes, I know it isn’t logically named, its been defined as 5001 ).   I’m just using netcat to send the UDP packets.   

 

Has anyone had luck getting UDP messaging working under lwip using the netconn api?  I’ve been fighting this for a couple of weeks now and have been able to send UDP packets, but never receive them properly.   I’m not sure what else to check.  The debug mode doesn’t really give much information, and stepping though with the debugger with the JTAGICE is also somewhat useless. 

 

Any insight would be oh so very much appreciated.  

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