UPnP

There are 2 reference implementations which both are based on 'Taipei Torrent'. This UPnP code is a fork mostly from the btcd one with some changes forked from tendermint.

• https://github.com/btcsuite/btcd/blob/master/upnp.go
• https://github.com/tendermint/tendermint/tree/master/internal/p2p/upnp

This library supports only IPv4 UPnP currently. The IPv6 UPnP protocol is specified here: http://upnp.org/specs/arch/UPnP-arch-AnnexAIPv6-v1.pdf

Other UPnP libaries to investigate:

• https://github.com/huin/goupnp
• https://gitlab.com/NebulousLabs/go-upnp (which is a wrapper around huins package)

Special Cases

FritzBox:

• Users must manually enable port sharing for the host. Otherwise the router returns XML error code 606.
• If the internal port is already forwarded under a different external port, error code 718 is returned.
• If the internal port is already forwarded under the same external port, it does not return an error.

Troubleshooting

Using Wireshark to intercept the UPnP request and response can help.

For Windows there is a UPnP tool here http://miniupnp.free.fr/files/. The tool supports listing existing mappings which is an interesting functionality. It would make sense to implement the list function to delete or reuse any existing mappings.