MqttJS-Unity error handling

[jimkberry]

The current build of Mqtt.JS is pretty sketchy with regard to error reporting for "expected" errors, things like: authorization failures or bad connection URLs. The is an onError hook, but for whatever reason it doesn't seem to fire for many of these situations, and for others it fires but returns nonsense error messages. (Tak a look at the Mqtt.JS repo issues for more details)

Anyway - I don't think it's worth holding up the rest of this project in order to try to find fixes/workarounds, but there at least should be an issue that tracks the status of these errors.

Connection errors:

• Bad protocol (really just "not ws or wss")
  exception fires inside mqtt.connect() but error object is "{ }"
• Bad host name
  mqtt.connect() succeeds and an exception fires afterward. Error object is {"isTrusted":true}
• Bad host address
• Bad port
• Bad user
• Bad pwd
• Bad path

[jimkberry]

Checked "bad protocol":

An exception fires inside js mqtt.connect() and C# OnError() callback is called,

Unfortunately the exception catch error param is an empty object: "{ }" so nothing can be inferred by the calling code.

Because the C#-land HasEverConnected property is false the handler assumes it's a connection error and just shuts everything down and reports "Connection Error"

a) Error is handled more-or-less properly
b) No hint at all as to what the problem was is returned.

[jimkberry]

Checked "bad hostname"

mqtt.connect() succeeds

exception is caught by client.stream.onError with error object: {"isTrusted":true} Um, what?!?!

C# OnError() is called and behaves more-or-less as above, so things kinda work out.

Once again: no clue as to what actually happened.