Implement MaxConns and MaxConnsPerHost to server

[jkralik]

MaxConnsPerHost optionally limits the total number of connections per host served by server(client).

MaxConns optionally limits the total number of connections served by server(client).

Zero means no limit.

[jdbruijn]

Hi @jkralik ,
I recently ran into a problem with usage of resources and would like to limit the number of simultaneous connections to the CoAP server. I found this issue but would like to know how much work it would be to implement this. Do you have an idea? I needed, I could help with the work to implement this.

[jkralik]

Hi @jdbruijn
I think it is no so hard to implemented. For UDP, DTLS, TCP-TLS you need to introduce counter of sessions and when it reaches the limit:

• For DTLS(https://github.com/go-ocf/go-coap/blob/418332224ecf267dbe11b8f34b64ec919d1c32a0/server.go#L571), TCP/TCP-TLS(https://github.com/go-ocf/go-coap/blob/418332224ecf267dbe11b8f34b64ec919d1c32a0/server.go#L650) you will stop accept new sessions(connections)
• For UDP(https://github.com/go-ocf/go-coap/blob/418332224ecf267dbe11b8f34b64ec919d1c32a0/server.go#L686) just drop packets from unknown sessions

and when some accepted session was closed, then you allowing accept of new sessions.