Users can specify rules using either a simple syntax or a full syntax. The simple syntax
only specifies the port and optionally the protocol to be allowed or denied on the host.
[...]
Example rules using the simple syntax:
ufw allow 53
This rule will allow tcp and udp port 53 to any address on this host. To specify a
protocol, append '/protocol' to the port. For example:
ufw allow 25/tcp
This will allow tcp port 25 to any address on this host.
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