hole-punch | A simple UDP-based NAT hole punching example for C | Networking library

by ckennelly C Version: Current License: BSL-1.0

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kandi X-RAY | hole-punch Summary

hole-punch is a C library typically used in Networking applications. hole-punch has no bugs, it has no vulnerabilities, it has a Permissive License and it has low support. You can download it from GitHub.

This repository contains a simple example of UDP hole punching in C. It compiles to two binaries, a server that relays client information and a simple client that ping-pongs data to and from another instance of itself. This protocol may fail when two clients are behind the same NAT and encounter a router that will not send packets to its own external IP address. This example is licensed under the Boost Software License 1.0. For more information see COPYING.

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hole-punch has a low active ecosystem.

It has 107 star(s) with 44 fork(s). There are 15 watchers for this library.

It had no major release in the last 6 months.

There are 1 open issues and 0 have been closed. There are no pull requests.

It has a neutral sentiment in the developer community.

The latest version of hole-punch is current.

Quality

hole-punch has 0 bugs and 0 code smells.

Security

hole-punch has no vulnerabilities reported, and its dependent libraries have no vulnerabilities reported.

hole-punch code analysis shows 0 unresolved vulnerabilities.

There are 0 security hotspots that need review.

License

hole-punch is licensed under the BSL-1.0 License. This license is Permissive.

Permissive licenses have the least restrictions, and you can use them in most projects.

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hole-punch releases are not available. You will need to build from source code and install.

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hole-punch Key Features

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hole-punch Examples and Code Snippets

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Community Discussions

Trending Discussions on hole-punch

UDP hole-punch explanation

UPnP hole punching can't use external IP to access device on local subnet

QUESTION

UDP hole-punch explanation

Asked 2022-Jan-08 at 05:10

I'm trying to understand UDP hole punching and I just don't quite get it. In concept it seems simple but when I put it into practice I can't pull it off. From what I understand there's a public server we call the hole-punch server. A client makes a request to hole-punch server (this is public). The hole-punch server spits out a public ip and port of the client that just made the request. So long as that port is open then essentially any random client can make a request to that client using that specific port and ip ?

The issue I guess I'm having is, the client is able to make a request to the server. The server is able to send data back to the client on that public port and ip however when another client tries to send a request to that client using that same port and ip it just doesn't go through and that's what's confusing me. If the server can make the request why can't another random client make that request?

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ANSWER

Answered 2022-Jan-08 at 05:10

The thing to know about UDP hole-punching is that many consumer-grade Internet routers/NAT-firewalls have a policy along the lines of "block any incoming UDP packets, except for UDP packets coming from an IP address that the user's local computer has recently sent a UDP packet to"; the idea being that if the local user is sending packets to a particular IP address, then the packets coming back from that same IP address are probably legitimate/desirable.

So in order to get UDP packets flowing between two firewalled/NAT'd computers, you have to get each of the two computers to first send a UDP packet to the other one; which is a bit of a chicken-and-egg problem since they can't know where to send the UDP packet without being able to communicate; the public server is what solves that problem. Since that server is public, both clients can communicate with the server (via UDP or TCP or HTTP or whatever), and that server can tell each client the IP address and port to send its UDP packets to. Once each client has sent some initial packets to the other, it should also (in most cases) then be able to receive UDP packets from the other client as well, at which point the server is no longer necessary as a go-between.

Source https://stackoverflow.com/questions/70629259

QUESTION

UPnP hole punching can't use external IP to access device on local subnet

Asked 2020-Feb-10 at 05:28

I have a somewhat unique situation where I require the ability to perform NAT hole punching for a multi node peer to peer type application; where all nodes must reference each other from publicly accessible IP addresses, even when some of those nodes might reside on the local subnet.

I have been able to successfully map ports with help from this question (UDP hole punching implementation) using Open.Nat.

My code is basically as simple as this:

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ANSWER

Answered 2020-Feb-10 at 05:28

This isn't really something you can fix, and it isn't really specific to C#. Most routers will only match NAT packets that arrive on their internet facing interface. If you want to allow for multiple nodes running behind the same NAT to connect directly to each other, you will need to implement another solution.

For example, you could share each node's private interface addresses. Then attempt to connect directly if the public address matches.

Source https://stackoverflow.com/questions/60096062

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