Infinite SSH tunnel

index.js

const { spawn } = require('node:child_process');

const user = 'user'
const password = 'password'
const ip = '1.1.1.1'
const port = 5173

let sshCommand = `-p ${password} ssh `
sshCommand += '-o ServerAliveInterval=5 '
sshCommand += `${user}@${ip} `

let forwardError = false

async function main () {
  const forwardCommand = sshCommand
    + `-R ${port}:localhost:${port} `
    + '-C -N -g -c [email protected] '
    + '-o ExitOnForwardFailure=yes '

  const tunnel = spawn('sshpass', forwardCommand.split(' '))
  tunnel.stdout.on('data', (data) => console.log(data.toString()))
  tunnel.stderr.on('data', data => {
    const err = data.toString()
    console.error('Error while connect:', err)

    // If port used, connect and kill process
    if (!forwardError && err.includes('remote port forwarding failed for listen port')) {
        forwardError = true
        console.log('Looks port used, connect and kill')
        const fuser = spawn('sshpass', [...sshCommand.split(' '), 'fuser', `-k ${port}/tcp`])
        
        fuser.stdout.on('data', (data) => console.log(data.toString()))
        fuser.stderr.on('data', data => console.error(data.toString()))
        fuser.on('exit', async code => {
          console.log(`Child exited with code ${code}`)
          
          if (code === 0) {
            console.log('Successfuly killed, wait 3000 ms and restart')
            await new Promise(r => setTimeout(r, 3000))
            main ()
          }
        })
    }
  })
  tunnel.on('exit', code => console.log(`Child exited with code ${code}`))
}

main ()

Requires sshpass, ssh, node16, also can be started with pm2