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.

Instructions for diagnosing a CTHL are located in the Support documents.

Error Messages

If you don't see these error messages, then you don't have a CTHL. You probably have a 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


We have several utilities which help determine the state of your connection to the game and possible sources of interference.



We will make a new, fixed version of CheckNet available as soon as possible.

CheckNet is a very simple application that attempts to perform simple network connections to several of the WWII Online game servers to determine (a) if you can reach them and (b) how long establishing the connection takes. The aim is to help you detect firewall or network connectivity issues which make affect or prohibit gameplay.


This little program written by our host programmer that will check your connection with packets of various sizes to see if there is a problem. Teultest Understanding Teultest Results


In your /Battleground Europe/ folder should be a file called wwiiol_netcheck.bat. When run, it will generate a new file called netcheck.txt. This file contains traceroutes to the game servers, your Settings choices, your DXDiag report (and if you're running WinXP Pro, a list of active processes running on your system).

In the traceroutes section, asterisks (*) indicated dropped packets and help to identify troublesome parts of connections. If you encounter a lot of these, you may need to contact your ISP to check for interference in your connection.

If you have the list of processes, you can see everything that is running and search the net for information on specific ones that you do not recognize. Of particular importance are programs that search the net for updates. These are often anti-virus and spyware security systems, but they can also be all kinds of other programs. Some of these can interfere greatly with your connection on a sporadic basis.

We recommend disabling programs that look for updates when trying to play Battleground Europe. In fact, we recommend terminating as many other applications as possible when playing to maximize your performance and stability.

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 (BitTorrent, shared folders on a network like PhotoShare)
  • 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

Software firewalls are often problematic and cause problems or interfere with game connections. We recommend avoiding them. The following ones specifically are known to cause connection problems for some users.

  • ZoneAlarm
  • nVidia nForce: known to cause a host of issues with TCP connections, and has proven highly problematic for WWII users.
  • Windows XP Firewall: :Disabling WinXP Firewall:
  • MS Quality of Service (QoS): By default Microsoft install and enable a QoS Packet Scheduler on all Windows XP network connections. It is highly recommended that you disable and uninstall this feature to generally improve your Internet access.

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.

Or something like that :P

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. Please use the Netcheck and Teultest utilities mentioned above.

Improving Connection Quality

There are three things you can do to improve your connection quality to our game (and two of them may improve your general internet connection quality). Items 2 and 3 may help reduce lag and/or frequent CTHL (Connection To Host Lost) errors.

1. Enable NetCode2

From the UI/Lobby select the SETTINGS tab. On the first page, bottom right, is an option for NETCODE2. This uses a completely different network protocol for certain data which should eliminate congestion problems with some ISPs.

Make sure your firewall/zonealert are flagged to allow WWII Online to use TCP and UDP ports 27015-27021.

2. Disable TCP Segmentation Offload in Windows

Some Network Interface Cards (NICs) and/or their drivers do not implement this relatively new Windows feature very well, which can introduce problems with some network traffic. Although this feature is enabled by default, Microsoft recommend disabling it on some 150 knowledgebase articles.

Windows XP Users:

Under the Start menu, select "Run". Enter ncpa.cpl and click ok

Right-click the network connection that you use for this network adapter, and then click Properties.

Click the "Configure" button at the top of the General tab.

Select the Advanced tab.

Select the option named "Offload Checksum" or "TCP Segmentation Offload" or "TCP Task Offload" and set the "Value" on the right hand side to "Disable"

Click OK and restart your computer.

3. Disable Large Send offloading

Some Network Interface Cards (NICs) and/or their drivers do not implement this relatively new Windows feature very well, which can introduce problems with some network traffic.

This feature is enabled by default but disabling it is often recommended. Leave this enabled until you have tried #2 and found that you are still experiencing frequent CTHLs.

Repeat the procedure described in Item 2, however the feature is called "Offload TCP_LargeSend".

After setting this to "Disabled" click OK and restart your computer.