problem to receive UDP package on client side

[Lintong Zhang]

Hi all,

I am new to LCM and networks,

Basically i can run server and receiver on the same local machine but problem appears when i run them on separate linux machines.

I followed the tutorial and set the socket adders as :  export LCM_DEFAULT_URL=udpm://239.255.76.67:7667?ttl=1 on both server and client terminal


Server IP address is 10.0.0.1 and client IP address is 10.0.0.2. They are connected by crossover cable and i can ping each other.

Server ifconfig output:

enp1s0    Link encap:Ethernet  HWaddr 00:07:32:3a:1f:43 
          inet addr:10.0.0.1  Bcast:10.0.0.255  Mask:255.255.255.0
          inet6 addr: fe80::ded:7fff:c644:288/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:103824 errors:0 dropped:0 overruns:0 frame:0
          TX packets:34364 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:30389670 (30.3 MB)  TX bytes:4761605 (4.7 MB)

lo        Link encap:Local Loopback 
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:103460 errors:0 dropped:0 overruns:0 frame:0
          TX packets:103460 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:8266465 (8.2 MB)  TX bytes:8266465 (8.2 MB)


when i run tcpdump on client side, the output is:

16:59:42.460310 IP 10.0.0.1.34107 > 239.255.76.67.7667: UDP, length 54
16:59:42.460365 IP 10.0.0.1.34107 > 239.255.76.67.7667: UDP, length 54
16:59:42.460406 IP 10.0.0.1.34107 > 239.255.76.67.7667: UDP, length 54
16:59:42.531642 IP 10.0.0.1.34107 > 239.255.76.67.7667: UDP, length 54

However , on server side, i dont see anything from tcpdump.

So why is the multicasting not getting though to client side pc?


Thank you very much

[Lintong Zhang]

i figured it out

Need to add right route ip address to the right interface.

In my case, i used enp1s0.

so it would  route add 224.0.0.0 netmask 224.0.0.0 enp1s0