fix handling closed socket

[piotr-karas]

Hi, I recently have encountered some problem with handling closed socket.

I had a lot of processes in my application and some of them have very often received 'eof' from socket (why this happend I'm not sure yet, probably it's something with system resources/connection speed/NATS server termination).
In most cases I have just received Server xyz closed the connection, but sometimes I got for example:
Invalid protocol MS or something like Unexpected error: Expected integer, but got "" while executing "incr expMsgLength 2".

Both this messages looked like we got only part of message while reading from socket. I have read about chan gets channelId ?varName? in the documentation and it says:

If an end-of-file occurs while part way through reading a line, the partial line will be returned (or written into varName).

So we actually can read part of message, if there was eof later, and treat it as a whole causing problem with handling it further. If we move eof check above that if statement, we will terminate it quicker and do re-connect without unexpected errors.

I have encountered this in old version, but I see that it is probably still here :)

Best regards

[Kazmirchuk]

Thanks for the PR!
Tcl documentation for non-blocking gets is very misleading if not outright wrong. I assumed that checking for $readCount <= 0 is enough to be sure I never get an incomplete line, but now I've experimented with it and see that it's not true.
Regarding frequent disconnections: could it be the 'slow consumer' problem? That your app receives more messages/sec than it can process, and then NATS server terminates slow connections? maybe you can see smth in NATS logs

[Kazmirchuk]

OTOH Ashok does mention this in his book on p.434:

Notice that on end of file, the buffered input content is delivered even though no newline characters were present.