In compliance with Chinese laws and regulations, players in Mainland China cannot connect to players on other regional servers.
We had to implement this in our server structure.
However, if you are in China and would like to play with someone who is not, or vice versa, Steam offers an easy trick to get around this.

In your Steam library, right-click on the game (either Operation: Tango, or Operation: Tango - demo)
This will open a pop-up menu
Click PROPERTIES
In the GENERAL tab, find LAUNCH OPTIONS
Input either one of these commands:
-forceChinaMode
or
-forceInternationalMode
The hyphen (-) is part of the command, it has to be typed in

The first command forces your game to behave as if it was in China. It will therefore connect to the Chinese servers so that you can play with a friend in China.
The second command does the opposite so that you can play with your friend outside of China.

Of course, the idea is that both players are considered in China, or both considered outside of China.

根据当地法律法规，中国大陆IP无法与其他地区玩家联网游玩。但是通过STEAM平台，我们可以通过如下方法解决联机问题：
-在steam库中右键点击《代号：探戈（Operation：Tango)》或好友通行证版本
-选择属性（PROPERTIES）—— 通用（GENERAL）——启动选项（LAUNCH OPTIONS）
-如果你的朋友是中国IP，你是海外IP，你可以在启动选项中输入 -forceChinaMode
如果你的朋友是海外IP，你是中国IP，你可以在启动选项中输入 -forceInternationalMode
（“-”符号必须输入，不可省略）

如有其它问题，欢迎给我们留言。