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TeamCity 2018.x Documentation

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A TeamCity agent connects to the TeamCity server via the URL configured as the "serverUrl" agent property. This is called unidirectional agent-to-server connection. If specifically configured, TeamCity agent can use legacy bidirectional communication which also requires establishing a connection from the server to the agents.
Unless security in transfer between the agent and the server is important, it is recommended to deploy agents and the server into a secure environment and configure agents to use plain HTTP URL for the server as this reduces transfer overhead.To view whether the agent-server communication is unidirectional or bidirectional for a particular agent, navigate to Agents | <Agent Name> | Agent Summary tab, the Details section, Communication Protocol.


Agents use unidirectional agent-to-server connection via the polling protocol: the agent establishes an HTTP(S) connection to the TeamCity Server, and polls the server periodically for server commands.

HTTPS agent-server connection

It is possible and recommended to set up a server to be available via the HTTPS protocol, so all the use HTTPS for agent to server communications (check related server configuration notes). If the agents and the server are deployed into a secure environment, agents can be configured to use plain HTTP URL for connections to the server as this reduces transfer overhead. Note that the data travelling through the connections connection established from an agent to the server (including the download of build includes build settings, repository access credentials and keys, repository sources, build artifacts, build progress messages and build log) can be secured. See Using HTTPS to access TeamCity server for configuration details.