There are multiple means of communicating between ships; depending on the equipment that each ship mounts, the nature of the communication, and the distance at which it must be conducted, different technologies are employed.
System to System
The only practical ways to get a message to another system are to either send a courier ship or get a relay station to send a message probe through the wormhole linking to that system. Some vessels carry their own message probes for work outside the relay network.
You need not contact that particular relay station directly, as relay stations throughout the Confederation are part of the above mentioned linked network. One need only contact the nearest or otherwise most convenient. This intermediate relay station will, based on the urgency of your message, use one of the following 4 methods to deliver it to the next relay in the system:
Emergency/Command and control communique priority
Using a modified mini-jump drive, a ship (almost exclusively a relay station, large vessel, or communications specialty ship, as smaller ships do not tend to have room to mount such) creates a small wormhole between its present location and the vicinity of its sender, and pulses the message through using standard Confederation EM frequencies. Highly energy intensive, but when time is of the essence, it's what you need.
Directed Burst Transmission
This is a normal transmission over standard EM frequencies as partitioned by the Confederation. Most communication takes place via laser-focused directional microwave antennae. As lasers have very low effective bandwidth, being mono-phase and mono-frequency, they are used only for calibrating the focus of the multi-phase, multi-frequency, multi-amplitude pseudo-parallel emission, directional microwave array.
Omni-Directional Burst Transmission
Same as above, except that everyone gets to hear it. Useful if you're on the cheap with comm equipment or just don't have a good lock on the location of the craft you're communicating with. Encryption is a must if you don't want the whole neighborhood to know what you're saying.
Spread Spectrum Omni-Directional Continuous Re-Transmission
Common uses: distress beacons/warning bouys/people who find an intense need to speak in ALL CAPS and feel that they can run away if anyone decides to express their annoyance.
- Is this currently modeled correctly in VS? No. I imagine parts of it (the relay network) will work their way in. Whether or not we'll introduce some form of light-lag for communications - who knows?