Kettle to pot, Hello? Come in, pot
Solution 1:
It's a reference to the proverbial idiom "The pot calling the kettle black". This has more recently been reworked into the simpler "pot, kettle" reference to invoke the idiom.
As others have noted, the "X to Y. Hello. Come in, Y." format is used to mimic the start of a radio conversation. It's used to get the listener's attention and is essentially saying "hey, are you listening?".
So, combined, "Kettle to pot. Hello. Come in, pot." is simply drawing attention to the fact that the person being spoken to is guilty of the same thing that they are accusing the speaker of.
Solution 2:
By the way . . .
The first translation of Don Quixote brought to England a proverb about a pot calling a kettle ‘black-eyes’. In less than twenty years it had been thoroughly Englished to become
The pot calls the pan burnt-arse.
It was then included in John Clarke’s 1639 collection of proverbs, Parœmiologia Anglo-Latina.
In conversation with his fellow prisoners, Cervantes himself probably said black-arse (culinegra in Spanish) rather than black-eyes (ojinegra). After all, whether it’s a pan or a kettle, black or burnt, it has no eyes, and what happens happens to its arse!
Changing social mores (probably Victorian ones) did for burnt-arse. Just as they did for white-arse, the apt name given to the upland bird now known as the wheatear, whose ears are nothing to write home about but whose white rump is conspicuous in flight. It is known in France as cul-blanc. No ‘épis de blé’ for them!
Solution 3:
"Come in, pot" is a play on words. You don't hear it much anymore, but in old TV shows (and probably radio before that), you would hear people (usually military or cops) on a two-way radio say something like:
"Car 17 to headquarters. Come in, headquarters."
when establishing a radio conversation.
And, of course, each side would say "Over" when they were finished speaking and ready for the other side to speak; "Over and out" when the conversation was done.