This is a tutorial on how to get multiplayer to work on Left 4 Dead: Survivors. This configuration is valid for all Co-Op categories. This is not a tutorial on how to configure the game to launch correctly, it assumes that you already know how to do that. This guide is split into three sections, based on which players need to perform the step in question (all players, host, and client).

For All Players

• Ensure that you're running on the same game version as everyone else. This is visible from the upper-left hand corner of the main menu. (This tutorial was tested in v1.26.)
• Download Hamachi and configure a virtual network. All players should be on the same virtual network. The person creating the virtual network does not need to be the host. If you receive an error when you attempt to ping another user, ensure that Hamachi Client Application is allowed to make public and private connections within your firewall software. If this still doesn’t work and you’re using Windows Defender Firewall, uncheck the Hamachi connection on the Secure Connections page of your current profile, under Windows Defender Firewall properties.
• Create a batch file or shortcut to launch the game, or edit an existing one, and add "-insecure +sv_lan 1 +sv_allow_lobby_connect_only 0" to it as launch options.
• Launch the game with these new launch options.

For The Host

• Open the console with "~" and type "net_status" to ensure the server is running. If not, use the net_start command.
• Type "map" into the console followed by the map name. (e.g. "map c1m1_hotel")

For The Client

• Right click on the host from the list of users in the Hamachi application, and select "Copy IPv4 address".
• While the host is loading into the level, open the console with "~" and type "connect" followed by the IPv4 address that you copied. You may time out if the host is still loading into the level, simply open the console and enter the command again.

Notes

• Clients will be disconnected when the host uses the "map" command to go to another level. You will have to reconnect again with the same command. You will not be disconnected when naturally moving between levels in a campaign.