The controller tries to send messages on FLOOD port that is an optional one and is NOT supported by OpenFlow-only switches. If a controller wants to use this port it should first make sure that the switch supports it. It can also use the ALL port that every OpenFlow-enabled switch is required to implement. See the OpenFlow 1.3.0 specification ch. 4.5.
The controller tries to send messages on FLOOD port that is an optional one and is NOT supported by OpenFlow-only switches. If a controller wants to use this port it should first make sure that the switch supports it. It can also use the ALL port that every OpenFlow-enabled switch is required to implement. See the OpenFlow 1.3.0 specification ch. 4.5.