How to close connection to a client?

[davidwaltre]

Hello,

I am using the library for a connection between two ESP8266 (one client, one broker). It works so far. (I'm also using the client from this library.)
But as soon as the client restarts, and tries to connect with the same ClientID, it disconnects again. After waiting four minutes, the broker disconnects the inactive client connection and the new client connects as it should.
(Same thing when the broker goes down, the client reconnects after some time has passed. Is that linked?)

I worked around this by using a randomly generated ClientID.

Now if the client restarts a couple of times, the broker has too many connections, to clients that are not in use anymore.

My idea: As I only every have one client in use with that broker, I wanted to close the previous client connection on every new connection.

My questions:

1. Why does the broker close the old connection and the client reconnect only after four minutes, and how can I change that time interval? Is that the time the client checks is the connection is still working, or is that broker-sided?

2. How can I close a connection to a specific client? Or close all current connections?

Thanks in advance!

[martin-ger]

Think, the problem could be, that the client doesn't terminate the MQTTT/TCP-session correctly. Thus the session stays alive untill the timeout happens. You say, the client "restarts". What happens here - does it close its TCP connection before restarting or is it just a reset?

[davidwaltre]

The client restarts through the reset button, or because it gets disconnected to power and reconnected later on. As I'm developing a relais on one of the ESP8266 that gets its commands from a button on the other ESP8266 and through a small one-button-website hosted on itself (I'll work on that website part later on), I think that the broker usually does not reset / restart.

My only concern now is that when the Client loses connection or resets, the broker will sooner or later have too many open connections so the Client can't connect anymore (using a random ClientID).

I'm thinking about restarting the broker when the Client connects a fourth/fifth time (with publishing a message before restarting - so the client knows it has to reconnect). In everyday use of the two components, I don't think the client will reset very often - but I also don't know for sure. And if it does reset, it most certainly can not close its connections due to the unforeseen resets.

Edit: As I thought about it, the dead connections are also dropped after four minutes. As the client probably doesn't reconnect that often in four minutes, I'll rely on that if I won't find any better solution.

[Sinix10]

Think, the problem could be, that the client doesn't terminate the MQTTT/TCP-session correctly. Thus the session stays alive untill the timeout happens. You say, the client "restarts". What happens here - does it close its TCP connection before restarting or is it just a reset?

Please, tell us how to change the "timeout" time, pls? I really need to change it.

Thanks

[martin-ger]

You will find the timeout values in "defaults.h".