tcp server

Node.js

const net = require('net')
function handler(socket) {
    socket.write('Received: ')
    socket.pipe(socket)
}
const server = net.createServer(handler)
server.listen(3000)

Output

$ echo 'hello' | nc localhost 3000
Received: hello

Go

package main
import (
    "bufio"
    "net"
)
func handler(conn net.Conn) {
    defer conn.Close()
    reader := bufio.NewReader(conn)
    for {
        message, err := reader.ReadString('\n')
        if err != nil {
            return
        }
        conn.Write([]byte("Received: "))
        conn.Write([]byte(message))
    }
}
func main() {
    listener, err := net.Listen("tcp", ":3000")
    if err != nil {
        panic(err)
    }
    defer listener.Close()
    for {
        conn, err := listener.Accept()
        if err != nil {
            panic(err)
        }
        go handler(conn)
    }
}

Output

$ echo 'hello' | nc localhost 3000
Received: hello