Sorry for the double post in such a short time frame. Please find at https://gist.github.com/thirtythreeforty/8b26cf6a9811fb638e55 a patch to the sample code icedemo.c that triggers the issue. Launch two copies of icedemo, connect them as usual, then run 'x' (send) from both; the payload does not matter. One should deadlock. As far as I can tell, full duplex should be allowed by pjlib. Is this not the case, or is it a bug in the library? George Hilliard