In 1935 Einstein and Rosen both at the Institute for Advanced Study in Princeton proposed the possibility of ‘wormholes’ that allow a non-rotating (Schwarzschild) black hole to bridge two separate points in spacetime. However such bridges can never be used because not even light could escape the event horizon. Then in 1963 Kerr found a set of solutions to Einstein’s field equations that describe a rotating black hole and this produced two event horizons; it was possible (in theory) to enter the first, miss the second (the killer) and exit back through the first to a separate point in spacetime.  

In Adrian Berry’s book (1977) The Iron Sun, he describes how this could be done and that’s where I got the idea of ‘instant communication’. Black holes rotate fast (1000 times per second for a hole with 10 solar masses.) so centrifugal force squashes them a lot. In fact they look like two DVD (one on top of the other) with a cherry through the centre and the channel between the two disks is the gateway to the wormhole.  
I use micro black holes (could be made in a powerful particle accelerator if involving extra dimensions of space) but they radiate so strongly that the life span is almost nothing! Therefor particles would have to be continuously beamed at the hole so they coalesce and that is the job of the Lorentz Fitzgerald Interstellar Transceiver balanced at the Lagrange point between Pluto and its moon Charon. However Berry admits that no one had figured out where the other end of the hole would end up, but there may be a way out of this predicament! 
In a 2020 article in Quanta Magazine Wormholes Reveal a Way to Manipulate Black Hole Information in the Lab ( it says – if I read it correctly – that if you quantum entangle to mini black holes information directed into one will appear instantaneously as Hawking radiation at the other irrespective of the distance between them , if the holes are over half their life span. So, entangle two holes (unfortunately I don’t know how) move one to another star and beam your information through the Einstein and Rosen bridge; voila! You have an Interstellar Transceiver. And here I leave it before I get more entangled myself!