There are phrases (and related verbs and nouns) that describe the first two such as give a holler
This is related to the verb holler
to shout or yell (something)
but it has a less excited quality, and is often used to refer to a greeting, and can even be used to convey contact me.
A similar term is give a shout. This also has a less urgent tone than the verb shout
These terms could be used to refer to electronic communication, but this usage is probably not very common. It has a bit of an oxymoronic quality (electronic amplification eliminates the need to holler or shout).
A related phrase specifically used on broadcast media is give a shout-out
a greeting, especially when someone on the radio sends the greeting to someone who might be listening
Another term commonly used for the electronic shout on a computer line to see if someone is there is ping
to send a test message to (a computer or server) in order to check whether it is responding or how long it takes it to respond