Using BusyBox version of netcat for listening tcp port
Here's the manual page for busybox's nc implementation.
The correct syntax is
nc -l -p <port>The issue is, I think, that your version of busybox is compiled without nc listening capabilities. Indeed there's a config option at build time, NC_SERVER, that needs to be enabled to turn that feature on.
Can you build another nc, perhaps from this version, and copy the binary onto your embedded host? You may need to build a cross-compiler environment.