Design

REPL wire protocol

Currently RemoteREPL uses the standard Serialization library to format messages on the wire because this is simple to use. However, this is not bidirectionally compatible between Julia versions so we'll probably move to a different message container format in the future.

RemoteREPL formats results as text (using show(io, "text/plain", result)) for communication back to the client. This is helpful because:

The result of a computation might be large, and it should be summarized before sending back. show is an excellent tool for this.
The remote machine may be a separate application with different modules loaded; it may not be possible to deserialize the results in the local Julia session when custom types are involved.

The standard streams

RemoteREPL doesn't interact with the standard streams stdout,stderr and stdin on the server. This avoids unexpected side effects such as interfereing with the server's normal logging and clashing with any concurrent RemoteREPL sessions.

However this means that RemoteREPL misses out on some behavior you'd expect from the normal REPL:

Functions like println() have side effects on the server which are not visible on the client. See the howto for how @remote(stdout) helps with this.
Interactive utilities like Cthulhu.jl — which reads from stdin and writes to stdout — don't work.

In future I hope to improve this situation with better stream forwarding utilities.