Is it possible to control which port the mackerel-agent uses? While it's not possible to control the port, we do support connection via proxy. For more information please refer to the section "I want to connect via HTTP Proxy." in the agent specs. Related articles The agent won’t startup. What is Mackerel's IP address and port number? How do the Mackerel and the mackerel-agent communicate? Is it possible to download metrics and monitors? Calculating the number of hosts