Running enode and node

Question

I am following this guide to set up Ethereum Proof of Authority on a VM in Azure. The guide says this about deploying a node, after setting up the enode.

--port 30311 is the enode port for node1 and has to be different from the bootnode port (that is 30310 if you followed my command) because we are on a localhost. On a real network (one node per machine), use the same port.

so in command prompt i did this

bootnode -nodekey boot.key -verbosity 9 -addr :30310

then i opened another prompt window to launch the node. using my public ip for rpc addr and using 30310 for the --port.

However i am bing given this message:

Fatal: Error starting protocol stack: listen udp :30310: bind: Only one usage of each socket address (protocol/network address/port) is normally permitted.

Why am i getting this message if there was written,

On a real network (one node per machine), use the same port.

n.b. im only deploying the enode and 1 node on this vm

Answer 1

You should set your bootnode to port 30311

bootnode -nodekey boot.key -verbosity 9 -addr :30311

and your "node 1" to port 30310

geth --datadir ~/eth-dev/ --identity 'node-nickname-here' --rpc --port 30301...

What the tutorial means by

On a real network (one node per machine), use the same port.

is that if you are you using multiple (virtual)machines to create your own network, you can use port 30310 for every node. Since you are only using 1 vm, you need to use a different port for each geth instance (node) you add to your network.