aprice / telnet

Go telnet library

Package telnet

The telnet package provides basic telnet client and server implementations for Go, including handling of IACs and extensible telnet option negotiation.

Currently both the basic client and server are implemented, as well as a NAWS client/server handler as a working example. Additional handlers may be added to the core library over time (feel free to submit a PR if you've written one you'd like to see added!)

Usage

Running a server:

svr := telnet.NewServer(":9999", telnet.HandleFunc(func(c *telnet.Connection){
	log.Printf("Connection received: %s", c.RemoteAddr())
	c.Write([]byte("Hello world!\r\n"))
	c.Close()
}))
svr.ListenAndServe()

The server API is modeled after the net/http API, so it should be easy to get your bearings; of course, telnet and HTTP are very different beasts, so the similarities are somewhat limited. The server listens on a TCP address for new connections. Whenever a new connection is received, the connection handler is called with the connection object. This object is a wrapper for the underlying TCP connection, which aims to transparently handle IAC. There is a slightly more complex example located in the example package.

Running a client is pretty simple:

conn, err := telnet.Dial("127.0.0.1:9999")

This is really straightforward - dial out, get a telnet connection handler back. Again, this handles IAC transparently, and like the Server, can take a list of optional IAC handlers. Bear in mind that some handlers - for example, the included NAWS handler - use different Option functions to register them with a client versus a server; this is because they may behave differently at each end. See the documentation for the options for more details.

Linereader

A sub-package, linereader, exposes a simple reader intended to be run in a Goroutine, which consumes lines from an io.Reader and sends them over a channel for asynchronous handling.