Thursday 5 July 2012

Wrestling with gevent-socketio

I just spent most of last week attempting to get gent-socketio to work. First problem that I ran into was that nobody seems to have used it with adobe flash based fallback on browsers that do not support websocket.   This method is referred to in the library as flashsocket.  I was pretty confident that nobody has tried it since the swf file required by was missing in the distribution.  I fixed that by checking in the swf file into the bit repo.   That was the easy problem to fix.

The second challenge was that has a concept of namespaces which are essentially logical boundaries r messages so that one physical connectioncan be multiplexed by multiple capabilities on a given page. There are two confusing concepts plus a potential bug that really confused me.  In the world you would use a namespace by specifying it in the io.connect() call on the client. Thus if you wanted to use the namespaces foo and bar. 

You would use the following code

fooconn =io.connect('')
barconn =io.connect('')

Now the confusing part is that the client library will use the host and port specified to connect to the server but would use the 'foo' /'bar' as the namespace as part of the protocol and the actual URL requested  on the server would be

If you want to change the URL you have to send a key:value pair as part of the connect call like so

fooconn =io.connect('', resource:"myurlprefix")

This will make the client library generate an URL of  and the namespace within the protocol would be 'foo'.  If you want to change the URL prefix then you have to change it on the server side as well. You do that by specifying the resource parameter on the server side if you are using a node.js server.  On python gevent-socketio libry theword resource is deprecated and you instead have to use the key 'namespace'!!! 

Well I just couldn't figure out all this complexity myself.  Thanks to Daniel Swarbrick who gave me some very detailed help I finally got my hands around the library. Thanks Daniel.

Hope this little explation gives you a background on what to look out for in gevent-socketio.  I will keep posting on any other gotchas that I runinto when I play with this library.

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