Add check of addresses on connection creation

[maxekman]

We stumbled upon an issue where the address for the transmitter was nil, which was unfortunately only detected at runtime (which in the case of the RD service meant that it was not detected on the HIL).

I suggest a "dummy" transmit or other check of the address on connection creation: https://github.com/einride/lcm-go/blob/master/transmitter.go#L75

The reason for the error and the fix, for reference: https://github.com/einride/rd/pull/264

[maxekman]

@Edholm Any thoughts on this?

[Edholm]

Hm yeah why not? Isn't the config required? Or why was it allowed to be missing? 🤔

[maxekman]

It was of type net.UDPAddr which can't be parsed by envconfig. netaddr.IPPort should be used instead, with a .UDPAddr() call to convert it where used. Very sneaky bug to find!