Connection To Host Lost

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A Connection To Host Lost, also known as a CTHL, occurs when your game client is unable to send or receive information to the game server. The game will hang with your ability to move being restricted, if a CTHL occurs you will be presented with a message that your connection to the host has been lost after ~40 seconds, during this ~40 seconds your game client is trying to reconnect to the game server. If you don't get the message, then the problem is not a CTHL strictly speaking.

Error Messages

If you don't see these error messages, then you don't have a CTHL. You probably have a Crash to Desktop (CTD). Connection To Host Lost 10057 Error

Not a CTHL

There are various problems that could appear to be a connection problem when attempting to login to the game server. Account problems Server could actually be down

Check the Announcements forum or the Tech Tips on the Support pages. Occasionally, we bring the servers down for campaign resets, and the odd technical problem.


If you have a firewall installed, it should come with a method for allowing access to various ports. Because the game sends and receives data, several ports on your system must be open to the game to connect to, otherwise you will not be able to connect to the servers correctly.

Firewall Ports

The game must have access to the following ports for acceptable gameplay:

TCP Ports UDP Ports
27015 27015
27016 27016
27017 27017
27018 27018
27019 27019
27020 27020
27021 27021

Things that Interfere


Some ISPs have don't like to move big packets back and forth to you as much as the game client does. To assist with connections that go through problematic ISPs, reduce your Visible Player Limit setting to Low (see below).

Routers & Firmware

  • LinkSys Wireless/Speedbooster Router Users Please contact LinkSys for advice on ensuring you have the latest Firmware on your router and for correctly setting the "Fragmentation Length" settings.
  • Belkin users: Some players have found the Belkin connection manager software interferes with their TCP connections in such a way as to cause CTHLs and other issues. Players found that uninstalling the manager software and only installing the drivers greatly improved their internet access and reduced or eliminated CTHLs in-game.


Problematic programs

  • file-sharing software
  • bandwidth 'accelerators'
  • network monitors
  • active virus scanners
  • programs look for updates all the time

Too Many Programs Running Too Many Connections Open 'Software Firewalls and Packet Schedulers

Game Settings

There are some game settings which can help your connection.

Visible Player Limit

This setting determines the size of information packets that are sent to you from the game server. Setting it to Low means smaller packets and this often helps with connections going through problematic ISPs, particularly when your connection is not broadband.

NetCode 2

This networking system has been integrated into the game. It is designed to assist players with the weakest of connections, mostly dial-up modem users. It only effect 'in-game' connections, i.e., once you are spawned into the world.

This option can be enabled in the in-game Preferences section. It is off by default.

Connection Choice

The Settings application and the in-game Preferences both allow you to choose which connection route you take to our game servers. CRS employs two connection routes, a Primary and a Secondary. For the vast majority of players, Use Best should always be used. However, when a persistent problem is evident on one path, we recommend choosing the superior route.

Miscellaneous Info

Why is it only WWIIOL that suffers these problems?

The foremost reason is that the PvP and Simulation nature of our product requires that we not allow any loss of data. For this reason we use the same, reliable, network protocol that applications such as web browsers and mail software use (TCP). Other games largely use a "lossy" protocol (UDP). As a result some of the hacks and tweaks that Web accelerators and some networking products employ to give the appearance of a faster internet connection can directly impact our product, usually by disabling or crippling the "good neighbor" aspects of the TCP protocol.

It's easy to compare our game against others such as Eve and WoW and find it wanting in certain aspects - both these games display similar concentrations of players to our game, and both of them have heavy PvP elements.

However, unlike our game, they both rely on targeting systems rather than player "twitch" skills, and neither of them is overly concerned with collision physics and concealment, so the accuracy with which you can see an enemy isn't of great concern. WoW simply sends vastly less updates as visible players increase, and Eve minimizes the number of potential updates that can be generated in any area by using simple trajectories for all moving objects, and severely limiting the frequency with which a player can change them.

Imagine if, as an infantryman, plane or tanker, you could only move by clicking the location on the ground you wish to move to, and only being allowed to enter a new click once every 5 seconds.

What is this QoS thing?

(Originally Posted by coombes) QoS i think means Quality of Service, its effectively an enforced cap on your network speed. Your over all network performance is a series of peaks and troughs, what QoS does is to slow you down to a speed of no higher than 1 of the troughs, so that as the network fluctuates you dont see any change.

Think of it like driving along a very hilly road flat out, say on the flat parts you can drive at 120 mph, 110mph up the hills and 130 mph coming down the other side. QoS is effectively a speed restrictor of say 105 mph. You the driver experience constant performance, even though it is below the potential of your vehicle.

I'm getting lag since this new update!

If this is the case, please review the advice and information above again. Most importantly, visit the "Network Route" option in our settings application to see if choosing the Primary or Secondary network specifically improves your connection and gameplay experience.

Also double check your firewall settings. When we release updates, some firewalls need to reauthorize the game to have the necessary access.

Packet loss at "demarc.cogentco."

When pinging our game servers, you will encounter 100% packet loss at an IP that has a name like "demarc.cogentco", or something like that. This is not actual packet loss. This is our firewall NOT letting you ping the game server.