A port number identifies a transport endpoint used by applications on a host. A server address can include an explicit port when a service uses one, while other URLs use the scheme's normal arrangement. Port information is separate from the account username, and the correct value must come from the actual service or network configuration.
A practical example
A service can issue an address containing a particular port for its supported endpoint. Pasting a different port found in another provider's guide may reach nothing or a different service even though the hostname and account details look otherwise familiar.
A common misunderstanding
Do not open inbound router ports simply because a player uses an outbound service port. The direction and purpose of the connection matter, and unnecessary forwarding can expose unrelated household services.
Related terms
Stable technical definition. Editorial approach