https://github.com/sergei-mironov/udprelay

Symmetrical UDP relay
https://github.com/sergei-mironov/udprelay

c mosh udp udp-ports udp-redirect udp-relay

Last synced: 5 days ago
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Symmetrical UDP relay

• Host: GitHub
• URL: https://github.com/sergei-mironov/udprelay
• Owner: sergei-mironov
• Created: 2019-09-15T17:45:36.000Z (about 5 years ago)
• Default Branch: master
• Last Pushed: 2022-04-12T08:55:43.000Z (over 2 years ago)
• Last Synced: 2024-07-07T11:28:52.182Z (4 months ago)
• Topics: c, mosh, udp, udp-ports, udp-redirect, udp-relay
• Language: C
• Homepage:
• Size: 6.84 KB
• Stars: 10
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
Udprelay

========

Udprelay implements a trivial symmetrical UDP relay. After start, it "opens" two

UDP ports and waits for clients. When clients are connected, the tool sends data 

received from one of them to another and vice versa.

Typical use case is to allow UDP clients behind different NATs to talk to each other.

One (and maybe the only) application is to help [Mosh](https://mosh.org) client

to connect to Mosh server behind NAT while staying behind another NAT. Details are

described in this StackOverflow [answer](https://stackoverflow.com/a/57948167/1133157).

Usage

=====

To build, just `make install`. The only mode of operation is:

```

$ udprelay bind-ip port-a port-b

```

where `bind-ip` is an IP to bind both ports to (like 0.0.0.0), `port-a` and `port-b` are UDP ports to

wait messages from.

Limitations

===========

* No security. The encription is up to user.

* Absolutely no security. Application doesn't attempt to track `port-a` and

  `port-b` remote credentials. Instead, it just sends one hand's data to the last

  seen address of another hand.

* Udprelay drops packets from one hand before it knows the remote credentials of

  the other hand.

  

Debugging

=========

The following tools may be usful:

* `strace`

* `tcpdump -i IFACE udp portrange PORTA-PORTB -vv -X -n`

Credits

=======

Based on `udp_redirect` C program by Ivan Tikhonov