Packages are not downloading through the CEM Internet Gateway. Error "Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host"

Products

• Client Management Suite

Issue/Introduction

Packages have stopped downloading through the Cloud-Enabled Management (CEM) Internt Gateway.  The Symantec Management Agent is communicating and policies and tasks are getting through, but the packages will not download unless the target is on the corporate network. 

When reviewing the Internet Gateway logs you will see the following error:

Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host. ---> System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host

Directly under that error message, you may see the following verbose message:

Only one usage of each socket address (protocol/network address/port) is normally permitted 

Environment

ITMS 8.6

Cause

The Internet Gateway service was hung

When troubleshooting this issue, and launching the Internet Gateway program, you may also receive an error stating: 

Internet Gateway Object reference not set to an instance of an object.

Resolution

Either restart the Internet Gateway or restart the Internet Gateway service and then make sure the Internet Gateway program is properly started.