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 What is Mackerel's IP address and port number? How do the Mackerel and the mackerel-agent communicate? The agent won’t startup. Calculating the number of hosts Is it possible to download various data that is registered in Mackerel in formats such as csv?