NIO+Multithreaded TCPSocket listener, very low cpu utilisation

kdevel kdevel at vogtner.de
Wed Nov 15 23:04:46 UTC 2017


On Wednesday, 15 November 2017 at 13:31:46 UTC, Daniel Kozak 
wrote:
> This one works ok for me, but I am on linux: 
> https://dpaste.dzfl.pl/f54decee45bc

It works, but it does not handle two connects in parallel. STR:

1. start the binary in console 1
2. telnet localhost 4444 in console 2
3. telnet localhost 4444 in console 3
4. enter a [RETURN] in console (3)

observed: nothing (the "thread" handling the first connect blocks)
expected: response

On my machine defaultPoolThreads() returns 1. This can easily be 
increased:

```
    defaultPoolThreads(8);
```

There is also another problem with Socket.select: It may return 
-1. This frequently happens when the ACCEPT socket is 
non-blocking and the select is interrupted (by the GC?) then 
errno == EINTR.

Also not having a timeout in the Socket.select of handle_socket 
allows for DOS attacks like the one above. In case of a timeout 
select also returns -1.


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