ARM MBED CoAP example mot opening port

Question

I have succesfully built the CoAP protocol example for ARM mbed ( https://developer.mbed.org/teams/sandbox/code/coap-example/file/0681e205d0e9/ ) on a K64F board. It comes out of the box, except for the server name (coap.me) changed to an internal IP address.

I see that it runs correctly and connects to the network:

[EasyConnect] Using Ethernet
[EasyConnect] Connected to Network successfully
[EasyConnect] IP address 192.168.1.15
[EasyConnect] MAC address 0e:43:54:d9:7c:71
Connected to the network. Opening a socket...
Calculated message length: 11 bytes
Starting server
Sent 11 bytes to coap://192.168.1.10:5683

I have set a computer that can connect to it. It can ping correctly to the board and I see that the ARP is negotiating with the correct MAC address.

I have launched an NMAP test and I see that the port is closed:

PORT     STATE     SERVICE
5683/udp closed    unknown

If I set a CoAP client in the computer (Copper) I see no connection in the terminal.

What I am missing?

Answer 1

Moving this to the answer section as well, in case someone else runs into this problem.

If you want to use an mbed OS 5 device as a UDP server , make sure to call .bind() on the socket.