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Magneon
Asked: 2016-03-09 09:50:23 +0800 CST

Why does tmux bind externally accessible ports?

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I am performing a quick audit of services listening on external interfaces on a Ubuntu 14.04 machine, and tmux is binding TCP *:50994 and *:59147 as reported by netstat -l.

I can connect to this port from another computer on the network (barring any firewall settings), but I can't find any documentation about why it's binding an external port. What is the purpose of this and is there a way to stop it?

tmux

2 Answers

  1. It is tmux and it is a Unix socket. Tmux apparently uses server sockets to allow for independent tmux servers to be run. man tmux

    Run tmux with no flags

    tmux

$ ss -l |grep tmux
u_str  LISTEN     0      128    /tmp/tmux-1000/default 62749                 * 0

    Then run tmux with -S /tmp/tmux.sock and see that the change in the socket path.

    $ ss -l |grep tmux
u_str  LISTEN     0      128    /tmp/tmux.sock 62765                 * 0

    Note, It is not TCP. This can be seen from using the flags -t (tcp) and -l (listening) 

    $ ss -tl
(returns no lines but the headers)
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  2. are you using tcsh? https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=204429 has a similar-ish problem where starting tmux on tcsh results in dns queries.

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