How to get remote addr and local addr when connected

[oyljerry]

Hi All:
After mqtt is connected, is there any way to get remote address (IP:Port) and local address (IP:Port) from this library? Thanks.

[MattBrittan]

The connection (client.conn) is not exported and no functions are currently provided that would give you access to the info you want - so no (providing access would introduce some complexity because the library supports automatic reconnections). I guess you could implement your own SetCustomOpenConnectionFn and get the info that way. This is something that could be added but seems pretty niche; may I ask what your use-case is?

[oyljerry]

Thanks for reply. Because I want to collect the information about current connection, So I need the remote address and local address.

"providing access would introduce some complexity because the library supports automatic reconnections" --> I think it can use a variable to store these, every time connected, refresh it. when disconnected, clear it.

[oyljerry]

@MattBrittan Is it ok to export client.conn, then others can use it to get more information about connection?

[MattBrittan]

No - it could not be accessed in a thread safe way (can be overwritten at any time by the reconnect code).

[oyljerry]

@MattBrittan I checked openConnection, I think here we just need to save (remoteAddr and localAddr) before return conn in it. It seems reimplement SetCustomOpenConnectionFn is a bit duplicate.

[MattBrittan]

Implementing the connection function involves a little bit of copying/pasting but is easily done within your own code. I'm reluctant to add complexity to the library for a fairly niche requirement when there is a workaround (you have not explained what you are using this info for so it's difficult to see if it would be of use to anyone else).

[oyljerry]

@MattBrittan I want this info is that the endpoint may have LB, and there are several IPs for it. So I want to get the remote addr and local addr of current MQTT connection. once more, It may be also useful when diagnostic network.

[MattBrittan]

I'm going to close this issue. There is a fairly simple work around (implement your own SetCustomOpenConnectionFn) and capture the address you want in that (this should only take a couple of minutes to do). The reasons I'm not adding this to the library are:

• Cost/Benefit - Adding this will complicate the library and be used by a very small number of people. As there is a simple way of implementing this yourself the change is not worthwhile.
• Thread safety - the connection may be dropped/re-established at any time. This means that this feature would require further synchronisation and is unlikely to be all that useful (because the address info may change immediately after you have read it). The upshot of this is the feature would really need to be implemented as a callback (and an existing callback can easily be utilised to achieve the desired result).