Seamless and non-seamless travel

In UE4, there are two main ways to travel: Seamless and non-seamless. The main difference, is that seamless travel is a non-blocking operation, while non-seamless will be a blocking call.

When a client executes a non-seamless travel, the client will disconnect from the server and then re-connect to the same server, which will have the new map ready to load.

It is recommended that UE4 multiplayer games use seamless travel when possible. It will generally result in a smoother experience, and will avoid any issues that can occur during the reconnection process.

There are three ways in which a non-seamless travel must occur:

• When loading a map for the first time
• When connecting to a server for the first time as a client
• When you want to end a multiplayer game, and start a new one

There are three main function that drive travelling: UEngine::Browse, UWorld::ServerTravel, and APlayerController::ClientTravel. These can be a bit confusing when trying to figure out which one to use, so here are some guidelines that should help:

UEngine::Browse

• Is like a hard reset when loading a new map.
• Will always result in a non-seamless travel.
• Will result in the server disconnecting current clients before travelling to the destination map.
• Clients will disconnect from current server.
• Dedicated server cannot travel to other servers, so the map must be local (cannot be URL).

UWorld::ServerTravel

• For the server only.
• Will jump the server to a new world/level.
• All connected clients will follow.
• This is the way multiplayer games travel from map to map, and the server is the one in charge to call this function.