You would have to save it in a variable or hard code it. msg #mychan %somevariable
Adding another /sock* command to the outline, if you're going to place your /sockopen command inside an event that has a $chan value (or inside an alias called from such an event), you could also /sockmark your socket with that $chan value right after opening it. Then you can call $sock($sockname).mark in subsequent socket events as required.
