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const ansi = require('./ansi')
const waitForData = require('./waitForData')
const EventEmitter = require('events')
module.exports = class TelnetInterfacer extends EventEmitter {
constructor(socket) {
super()
this.socket = socket
socket.on('data', buffer => {
if (buffer[0] === 255) {
this.handleTelnetData(buffer)
} else {
this.emit('inputData', buffer)
}
})
this.initTelnetOptions()
}
initTelnetOptions() {
// Initializes various socket options, using telnet magic.
// Disables linemode.
this.socket.write(Buffer.from([
255, 253, 34, // IAC DO LINEMODE
255, 250, 34, 1, 0, 255, 240, // IAC SB LINEMODE MODE 0 IAC SE
255, 251, 1 // IAC WILL ECHO
]))
// Will SGA. Helps with putty apparently.
this.socket.write(Buffer.from([
255, 251, 3 // IAC WILL SGA
]))
this.socket.write(ansi.hideCursor())
}
cleanTelnetOptions() {
// Resets the telnet options and magic set in initTelnetOptions.
this.socket.write(ansi.resetAttributes())
this.socket.write(ansi.showCursor())
}
async getScreenSize() {
this.socket.write(Buffer.from([255, 253, 31])) // IAC DO NAWS
let didWillNAWS = false
let didSBNAWS = false
let sb
inputLoop: while (true) {
const data = await waitForData(this.socket)
for (const command of this.parseTelnetCommands(data)) {
// WILL NAWS
if (command[1] === 251 && command[2] === 31) {
didWillNAWS = true
continue
}
// SB NAWS
if (didWillNAWS && command[1] === 250 && command[2] === 31) {
didSBNAWS = true
sb = command.slice(3)
continue
}
// SE
if (didSBNAWS && command[1] === 240) { // SE
break inputLoop
}
}
}
return this.parseSBNAWS(sb)
}
parseTelnetCommands(buffer) {
if (buffer[0] === 255) {
// Telnet IAC (Is A Command) - ignore
// Split the data into multiple IAC commands if more than one IAC was
// sent.
const values = Array.from(buffer.values())
const commands = []
const curCmd = [255]
for (const value of values) {
if (value === 255) { // IAC
commands.push(Array.from(curCmd))
curCmd.splice(1, curCmd.length)
continue
}
curCmd.push(value)
}
commands.push(curCmd)
return commands
} else {
return []
}
}
write(data) {
this.socket.write(data)
}
handleTelnetData(buffer) {
let didSBNAWS = false
let sbNAWS
for (let command of this.parseTelnetCommands(buffer)) {
// SB NAWS
if (command[1] === 250 && command[2] === 31) {
didSBNAWS = true
sbNAWS = command.slice(3)
continue
}
// SE
if (didSBNAWS && command[1] === 240) { // SE
didSBNAWS = false
this.emit('screenSizeUpdated', this.parseSBNAWS(sbNAWS))
this.emit('resize', this.parseSBNAWS(sbNAWS))
continue
}
}
}
parseSBNAWS(sb) {
const cols = (sb[0] << 8) + sb[1]
const lines = (sb[2] << 8) + sb[3]
return { cols, lines, width: cols, height: lines }
}
}
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