I am in the process of setting up my first Tor Bridge:

Bridge <firgerprint redacted> advertises:

* obfs4: functional
  Last tested: 2023-08-12 03:23:02.954463531 +0000 UTC (43m55.667246855s ago)

I followed the official instructions for Ubuntu-based OS.

One thing I do not understand, maybe for someone else it could be self-explanatory, but it sure isn't to me:

Why do I need to have 2 different ports open and not just one? What makes them different?:

 1071  476K ACCEPT     tcp  --  any    any     anywhere             anywhere             tcp dpt:4xxxx /* Tor Bridge (Onion) */
47256   13M ACCEPT     tcp  --  any    any     anywhere             anywhere             tcp dpt:4yyyy /* Tor Bridge (obfs4) */

Well, as shown above, more packets/data flows through the obfs4 port, but feel free to elaborate and explain. Thanks.

1 Answer 1


The onion port is for Tor's network itself - and you always need it to be opened, so the other members of the network can reach you. The Bridge port is where the pipelining happens: the connection is accepted from the client that is not a network member yet, but wants to connect to. It's pipelined through the pluggable transport to scramble/unscramble the native Tor network protocol - so it's not visible to the censors that it is, but visible to the local Tor instance of the bridge.

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