For reference (we have been emailing) - you are getting the IOError because you are not using the full path to the SWF.
file=/anim.swf
should be something like:
file=/Users/username/documents/work/stuff/apps/swf/renderer/test/osxcli/anim.swf
and
exportPath is the full path to the folder where you would like to save the sequence to.
This command worked for me:
curl -d 'command=render,file=/Users/username/documents/work/stuff/apps/swf/renderer/test/osxcli/anim.swf,exportPath=/Users/username/documents/work/stuff/apps/swf/renderer/test/osxcli/,stopMode=0,stopTime=5,fileName=anim,exportFormat=MP4Exporter' http://192.168.0.7:8888/
curl -d 'command=startRender' http://192.168.0.7:8888/
Also note:
I used: stopMode=0 <--- to stop after a specified amount of time has elapsed ( instead of last frame as your SWF is 1 frame long )
and, stopTime=5 <--- for 5 seconds of rendering
Please let me know if this helped.