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?

  • Is lsof part of that version of busybox? – Zoredache Jan 7 '11 at 21:07
  • Unfortunately not. – a1337q Jan 7 '11 at 21:10

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.)


$ 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.

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  • Sounds cool, but my netstat doesn't work as it should, it outputs nothing additional with the -e option. I have 6 columns also with -e: Proto, Recv-Q, Send-Q, Local Address, Foreign Address, State. Is there a way with the ports? I can see the port.. – a1337q Jan 7 '11 at 21:05
  • You're right, I must have messed up my tests. I edited it to give you a working solution. – Peter Eisentraut Jan 8 '11 at 8:39
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    How do you find the number "2560" you type in your second command? That's the question. – ygoe Mar 22 '19 at 11:17
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    @ygoe you have to use 6115 and use it like this: find /proc/ -type l | grep /fd/ | xargs ls -la 2>/dev/null | grep 6115 – Sam Jun 27 '19 at 12:44

This may not help, if you don't have the opportunity to rebuild Busybox, but in case it helps anyone...

Busybox does have a configuration option to support the -p switch of Busybox netstat. See option CONFIG_FEATURE_NETSTAT_PRG, selected in busybox menuconfig via Networking Utilities → netstat → Enable PID/Program name output.

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If you have or can get ss on your device it can show you the PID too:

ss -ltp # for TCP
ss -lup # for UDP
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