Why did Kino strike the gate?

Kino struck the gate to alert the doctor. He was desperate and angry all at the same time.

He could kill the doctor more easily than he could talk to him, for all of thedoctor's race spoke to all of Kino's race as though they were simple animals. And as Kino raised his right hand to the iron ring knocker in the gate, rage swelled in him, and the pounding music of the enemy beat in his ears, and his lips drew tight against his teeth - but with his left hand he reached to take off his hat. The iron ring pounded against the gate.