chatServer.go

package main

import (
	"net"
	"bufio"
	"log"
    "fmt"
)

type client chan<- string // an outgoing message channel
var (
	entering = make(chan client)
	leaving = make(chan client)
	messages = make(chan string) // all incoming client messages
)

func main() {
	listener, err := net.Listen("tcp", "localhost:8000")
	if err != nil {
		log.Fatal(err)
	}

	go broadcaster()
	for {
		conn, err := listener.Accept()
		if err != nil {
			log.Print(err)
			continue
		}
		go handleConn(conn)
	}
}


func broadcaster() {
	clients := make(map[client]bool) // all connected clients
	
	for {
		select {
			case msg := <-messages:
				// Broadcast incoming message to all
				// clients' outgoing message channels.
				for cli := range clients {
					cli <- msg
				}
			case cli := <-entering:
				clients[cli] = true
			case cli := <-leaving:
				delete(clients, cli)
				close(cli)
		}
	}
}


func handleConn(conn net.Conn) {
	ch := make(chan string) // outgoing client messages, ch is the new client
	go clientWriter(conn, ch)
	who := conn.RemoteAddr().String()
	ch <- "You are " + who
	messages <- who + " has arrived"
	entering <- ch
	input := bufio.NewScanner(conn)
	for input.Scan() {
		messages <- who + ": " + input.Text()
	}
	// NOTE: ignoring potential errors from input.Err()
	leaving <- ch
	messages <- who + " has left"
	conn.Close()
}


func clientWriter(conn net.Conn, ch <-chan string) {
	for msg := range ch {
		fmt.Fprintln(conn, msg) // NOTE: ignoring network errors
	}
}