The number of devices that can simultaneously connect remotely to a cMT product (using cMT-Viewer, cMT-Viewer app, or EasyAccess 2.0) is controlled on the <i>remote</i> tab of the System Parameter Settings window in EasyBuilder Pro (Home > System Paramters… > Remote):

The default number is 3 and the max is 10. Connecting with multiple devices will increase the bandwidth requirement and CPU load on the cMT and could affect performance.