Use Jami on a LAN
Due the distributed nature of Jami, it is possible to use it over a LAN, without any Internet connection. This allows you to continue to communicate with other people in the company/building/country without global Internet access. However, some services are external so in this document we will explain some tweaks you may need.
Jami uses the DHT technology to find other users. So, all the users you want to contact must be reachable on the same DHT network (e.g. if the Internet is split between two buildings, users in the first buildings will not be able to reach the second building). To enter a DHT network, one must be able to reach at least one other node. This node is called bootstrap, it is the entry point of the network. By default, bootstrap.jami.net is configured, but any node in the public DHT can be a bootstrap (it is a classic node, generally always online).
So, if the Internet is cut, you need another bootstrap to create a network. On a LAN, there is two ways to configure it in Jami:
In the advanced account settings, the user can configure multiple bootstraps. bootstrap.jami.net is usually the default, bootstrap.jami.net;your.bootstrap.tld will be valid. The IP:port of another DHT node can be specified as a bootstrap.
Another way is to enable peer discovery. This will announce the bootstrap on the network by broadcasting UDP packets (like a printer). So, UDP broadcast must be supported by the network in order to work. However, this method does not need to specify an ip:port in the settings, so it can be preferred.
Another external service is the TURN server, used as a fallback for connections if the NAT block all possible connections. Generally it is turn.jami.net but can be any TURN (we use coturn, cf. Setting up your own TURN server)
On a LAN, it may be ignored (because there will be no NAT), but disabling it should not be necessary (because it will not be used if unreachable).
A DHT Proxy is used with mobile devices to save battery by avoiding synchronization. It is generally dhtproxy.jami.net but can be any DHT node with the REST API enabled. However, if the DHT proxy is using push notifications it will depend on another external service (Firebase or APN or a Unified Push instance). In this case, only the third one can be self-hosted.
On iOS it is basically not possible to work without push, as the OS from Apple will kill any application as soon as it is in background. So you can not disable the usage of push notifications. However, for Android, you may want to self-host your proxy (with or without unified push support), or you can disable the DHT Proxy and enable “Run in background” in order to use your local DHT.
Finally, the last external service you may need is a NameServer. This is used to translate addresses (the 40-characters fingerprint ID) to usernames. You may not have access to ns.jami.net, but you can self-host one (Name Server protocol) or only use IDs.