NodeJS TCP half-close

half-close.js

const net = require('net')

const server = net.createServer({ allowHalfOpen: true }, (socket) => {
  socket.on('data', (data) => {
    console.log('Server <-', data.toString())
    if (!socket.writableFinished) {
      socket.write('hello')
      console.log('Server -> hello')
      // half-close
      socket.end()
      console.log('Server -> FIN')
    }
  })
  socket.on('end', () => {
    console.log('Server <- FIN -> ACK')
    if (!socket.writableFinished) {
      socket.write('afterword')
      console.log('Server -> afterword')
      socket.end()
    }
  })
})

server.listen(8080, () => {
  console.log('Server listening on port 8080')
})

// ----------------------------------------------------

const client = net.createConnection({ port: 8080, allowHalfOpen: true }, () => {
  client.write('hello')
  console.log('Client -> hello')
  // half-close
  // client.end()
  // console.log('Client -> FIN')
})

client.on('data', (data) => {
  console.log('Client <-', data.toString())
})

client.on('end', () => {
  console.log('Client <- FIN -> ACK')
  if (!client.writableEnded) {
    client.write('afterword')
    console.log('Client -> afterword')
    client.end()
  }
})