# Processing the errorArray-subset returned by IO.select() **URL:** \ **Category:** Ruby\ **Created:** [March 4, 2009, 10:41pm UTC](https://www.ruby-forum.com/t/processing-the-errorarray-subset-returned-by-io-select/162014 "2009-03-04T22:41:51Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![Sebastien\_Raveau](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/9de053/32.png) [@Sebastien\_Raveau](https://www.ruby-forum.com/u/Sebastien_Raveau)\ **Post date:** [March 4, 2009, 10:41pm UTC](https://www.ruby-forum.com/t/processing-the-errorarray-subset-returned-by-io-select/162014/1 "2009-03-04T22:41:51Z")
Hi everybody! I am posting my question to this list really as a last recourse after having duly searched Ruby’s doc, Google, Ruby’s source, IRC, etc… Can somebody please end my torment? What I’m trying to achieve is a fully asynchronous HTTP proxy (or, for the sake of simplicity let’s just say a TCP relay between A and B) in just one thread, meaning: - when I non-blockingly (select+accept) get a new connection from A, I have to open the relay connection to B using connect\_nonblock - upon “readable” events on sockets belonging to either A or B, I must non-blockingly write() to the other (or cache the data and wait for the other socket to be “writable”) - have to teardown the relay as soon as any side shows signs of connect timeout, close, reset, etc Now, in order to monitor socket status I cannot rely on begin/rescue/end (actually I found a tutorial where the author calls connect\_nonblock a second time and checks EISCONN to see if the socket connection was successful, but that’s not the best way to do it, is it?), so I thought my answer was in the third array returned by select, concerning socket errors/exceptions… but I cannot find any documentation on that, and everybody seems to call IO.select() with ‘nil’ as third argument :-/ Does anybody know how to process it? Is there a way to get the corresponding Errno for each socket? Thank you 🙂