I need to listen some arbitrary port inside the Linux embedded box. I chose port 6660 because it is meant for uncrypted connections anyway and since the Linux box running customized Linux OS there are not many ports open. I found out that netcat (nc on command line) would be the easiest and the best ready to go solution for that, so I do not have to start programming some C program for that purpose.
I managed to grasp the command and options and I implemented simplest way to listen plain text on my PC from another PC like this:
sven@sven:~$ nc 192.168.4.110 6660 sven@sven:~$ hello there! anotherUser@userg:~$ nc -l -p 6660 anotherUser@userg:~$ hello there! But the case is that the netcat tool is coming with the busybox package on that Linux box. And I am not sure what would be the syntax how to listen a port (6660 for example). I always get the same dialog:
~ # nc -l -p 6660 BusyBox v1.17.1 (Debian 1:1.17.1-8) multi-call binary. Usage: nc [IPADDR PORT] Open a pipe to IP:PORT Also I've tried many other ways how to implement listening but cant get it done. I assume at least it would give me any options? also
nc -h or
nc --help dont give any "minus" options
But sending the text from Linux embedded box to my PC works:
~ # nc 192.168.4.130 6660 fsdf tere ^C ~ # sven@sven:~$ nc -l -p 6660 fsdf tere Linux embedded box has fully functional net connection inside the same local network and has existing eth0 and lo links
eth0 Link encap:Ethernet HWaddr D0:E3:47:00:03:5F inet addr:192.168.4.179 Bcast:192.168.4.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:28046281 errors:0 dropped:0 overruns:0 frame:0 TX packets:428464 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:2458890234 (2.2 GiB) TX bytes:83021395 (79.1 MiB) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:2282 errors:0 dropped:0 overruns:0 frame:0 TX packets:2282 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:444956 (434.5 KiB) TX bytes:444956 (434.5 KiB) Töövõite!
1 Answer
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.
