tcpproxy.ts

import net = require("net")
import sni = require("sni")
const TCP_PORT = 443
const PORT = "8444"
const CERT_PORT = "8445"
const remotehost = "localhost"
const remoteport = parseInt(PORT, 10)
const remoteCertHost = "localhost"
const remoteCertPort = parseInt(CERT_PORT, 10)
const log = (...str) => {
  console.log(...str)
  // do nothing
}
const tcpServer = net.createServer(localSocket => {
  const remotesocket = new net.Socket()
  localSocket.once("data", data => {
    const host = sni(data)
    if (host.includes("cert")) {
      remotesocket.connect(remoteCertPort, remoteCertHost)
    } else {
      remotesocket.connect(remoteport, remotehost)
    }
  })

  localSocket.on("data", data => {
    if (remotesocket.writable) {
      const flushed = remotesocket.write(data)
      if (!flushed) {
        log("  remote not flushed; pausing local")
        localSocket.pause()
      }
    }
  })

  remotesocket.on("data", data => {
    const flushed = localSocket.write(data)
    if (!flushed) {
      log("  local not flushed; pausing remote")
      remotesocket.pause()
    }
  })

  localSocket.on("drain", () => {
    remotesocket.resume()
  })

  remotesocket.on("drain", () => {
    localSocket.resume()
  })

  localSocket.on("close", had_error => {
    remotesocket.end()
  })
  localSocket.on("error", err => {
    console.log("localSocket", err)
    localSocket.end()
  })
  remotesocket.on("error", err => {
    console.log("remotesocket", err)
    remotesocket.end()
  })
  remotesocket.on("close", had_error => {
    localSocket.end()
  })
})
const tcpInstance = tcpServer.listen(TCP_PORT, () => {
  const { address, port } = tcpInstance.address() as net.AddressInfo
  log(`Tcp server listening on ${address}${port}`)
})