Is the Java Websockets send method async or does it wait?

Question

I am using the Java Websockets library from https://github.com/TooTallNate/Java-WebSocket. I would like to calculate the latency between sending messages. When using the send(message); function, will that wait until the server receives the packet (since it uses TCP), or does it just finish the method in it's own thread.

Thanks!

@Jim Garrison, well I have googled, and looked at the source. But could not find a definite answer. — Ajay, Jan 08 '17 at 23:02
It should be pretty easy to step through the code and figure this out. Since the library is implemented using NIO, I would expect it to provide both options. — Jim Garrison, Jan 08 '17 at 23:03
@JimGarrison I have and see no proof of it not waiting, but would like to confirm it with someone who knows for sure. — Ajay, Jan 08 '17 at 23:06

user207421 · Accepted Answer · 2017-01-09T01:29:31.590

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When using the send(message); function, will that wait until the server receives the method

That statement doesn't even make sense. The server doesn't receive the method, it receives the data the method sends.

(since it uses TCP)

There is nothing in the TCP API that waits for the peer to receive anything. When you send data via TCP, it is buffered in the local socket send buffer and returns immediately. The actual data is sent to the peer asynchronously over the network. The send blocks while the send buffer is full if the underlying socket is in blocking mode (the default), otherwise it either returns a short send return code in non-blocking mode, or posts a Future of some kind in asynchronous mode. Your question may really be about which of these modes the underlying socket is in, or not.

or does it just finish the method in its own thread.

It always does that in any of the modes.

edited Jan 09 '17 at 01:29

answered Jan 09 '17 at 01:03

user207421

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Thanks for the info, I was thinking it would wait, because I know in TCP, unlike UDP, it makes sure the packets are delivered. – Ajay Jan 09 '17 at 01:15
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@Ajay It does but it doesn't delay the application in doing so. – user207421 Jan 09 '17 at 01:27
Ok, thanks. That makes ping a little harder to calculate then. – Ajay Jan 09 '17 at 01:28
By the way, I edited the first quote in my question. – Ajay Jan 09 '17 at 01:44

score 0 · Answer 2 · answered Jan 09 '17 at 00:29

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Turns out it is a

non-blocking event-driven model (similar to the WebSocket API for web browsers).

This is found from the README.MD here: https://github.com/TooTallNate/Java-WebSocket

answered Jan 09 '17 at 00:29

Ajay

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That doesn't really answer the question you actually asked. – user207421 Jan 09 '17 at 01:04
@EJP it is because the question was about this library specifically. – Ajay Jan 09 '17 at 01:25

Is the Java Websockets send method async or does it wait?

2 Answers2