allow client-side port or port range to be specified

[ott2]

It would be useful if mosh allowed the client port, or port range, to be specified. The envisaged scenario is something like:

1. set up firewall to pass through UDP port 60001
2. mosh -p 60001 -P 60001 server.example.com.

or with port ranges:

1. set up firewall to pass through UDP ports 6[01]000
2. mosh -p 60000:61000 -P 60000:61000

Mosh currently uses a system-assigned port number for mosh-client. It is therefore not possible to tunnel mosh through stateless firewalls, unless they are set up to allow essentially all UDP through.

(This scenario is common for DNS. For instance, a BIND name server can be configured to always use source port 53 when acting as a client, allowing a port 53-only UDP pass-through on the firewall.)

The code for server-side port ranges is already in place, via try_bind(), although this is not currently exposed to the user. What seems to be required is a modification to the client's Connect() to call try_bind() with a port or port range, if specified.

[yaniv-aknin]

+1

[JustRamires]

I've tried to modify source code(https://github.com/JustRamires/mosh/commit/3d0381938573c0f7ced3a201e916c3946fc1300c). But when I try to start mosh-client I get the "MOSH_KEY environment variable not found" error. And I can't change mosh because I don't know Perl(The script doesn't pass the port range to mosh-client). How can I test my changes?

[sinkers]

+1 Mosh looked cool but without a way to get through a firewall it makes it pretty much unusable in a corporate environment

[andersk]

Duplicate of #296 (now closed).

[cgull]

Actually, this is not a duplicate of #296; that's about specifying a server side port range, this is about specifying a client side port or port range.

[eminence]

530 is one solution (though it doesn't expose a command line parameter like this issue suggests)

[achernya]

Adding a --client-bind= would be a reasonable spelling.