Transports
Transports are roughly analogous to Ring’s adapters: they provide an
implementation of a common protocol (nrepl.transport.Transport)
to enable nREPL clients and servers to send and receive messages without regard
for the underlying channel or particulars of message encoding.
nREPL includes two transports, both of which are socket-based: a "tty"
transport that allows one to connect to an nREPL endpoint using e.g. telnet
(which therefore supports only the most simplistic interactive evaluation of
expressions), and one that uses
bencode to encode
nREPL messages over sockets. It is the latter that is used by default by
nrepl.server/start-server and nrepl.core/connect.
TTY Transport
Using the TTY transport is pretty simple. You just need to start an nREPL server with TTY transport and you’re good to go:
(require
'[nrepl.server :as server]
'[nrepl.transport :as transport])
(server/start-server :port 12345 :transport-fn transport/tty :greeting-fn transport/tty-greeting)
The :greeting-fn is responsible for printing the initial message you’ll see
upon connecting.
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Afterwards you can simply connect to the server with some TTY client like telnet, nc or inf-clojure.
$ nc localhost 12345
;; Clojure 1.9.0
user=>Starting with nREPL 0.5 you can also start an nREPL with a TTY transport using clj:
$ clj -R:nrepl -m nrepl.cmdline -t nrepl.transport/tty
nREPL server started on port 63266 on host localhost - telnet://localhost:63266Bencode Transport
There’s nothing special you have to do to use the bencode transport,
as it’s the default transport for nrepl.server/start-server.
You’ll need a bencode capable client to connect to an nREPL server that transport.
nREPL’s bencode implementation is available as a standalone library.
Keep in mind that nREPL itself doesn’t use this library, as it’s committed to having 0 runtime dependencies.
The code in the library and in nREPL nrepl.bencode namespace in identical, though, and will be kept in sync
in the future.
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