When a Silk Test Classic agent cannot run on the same machine as the Silk Central execution server, for example when tests are run on platforms other than Windows, the hostname and port may be specified by the Silk Test Classic AUT Hostname setting in the Deployment page of an execution plan. If the setting has not been defined, Silk Test Classic default values are used, for example from partner.ini. The syntax for AUT is hostname:port. The agent must be started manually prior to test execution and configured to listen at the specified port. By default, the TCP/IP protocol is used for communication between Silk Test Classic instances and Silk Test Classic agents. Ensure that both programs have been configured to use the same protocol.