Busybox, netstat, no -p

Question

I have an ultra old (don't ask why) BusyBox (BusyBox v1.01 (2008.12.19-21:31+0000) Built-in shell (ash)) on my DreamBox. I would like to find out which process opened which connection using netstat. But I found out that BusyBox's netstat doesn't contain the -p option. What other possibilites do I have to find out which process has opened (and is using) the corresponding socket?

Answer 1

You can find the equivalent information in slightly uglier form (a.k.a. hexadecimal) in /proc/net/tcp. There, you can find the inode of the connection, which you can look up under /proc/$pid/fd/.

For example:

$ cat /proc/net/tcp
sl  local_address rem_address   st tx_queue rx_queue tr tm->when retrnsmt   uid  timeout inode
 0: 00000000:0016 00000000:0000 0A 00000000:00000000 00:00000000 00000000     0        0 6115 1 f5adc4c0 300 0 0 2 -1
...

(In normal netstat, but not in busybox netstat, the -e option also gives you that extra information.)

and

$ sudo ls -l /proc/2560/fd
...
lrwx------ 1 root root 64  7 jan 22.50 3 -> socket:[6115]

You need root access for the second step.

Not as convenient as the -p option, obviously, but works in a bind. Could be scripted, if necessary.