From 4e38318564b4fe27225a56b853b1844270a26394 Mon Sep 17 00:00:00 2001
From: Alexander Munch-Hansen <alexmunchhansen@gmail.com>
Date: Mon, 7 Sep 2020 17:20:48 +0200
Subject: [PATCH] Programming exercises from week 1

---
 week_1/exercise-2-2-client.go | 52 +++++++++++++++++++++
 week_1/exercise-2-2-server.go | 85 +++++++++++++++++++++++++++++++++++
 2 files changed, 137 insertions(+)
 create mode 100644 week_1/exercise-2-2-client.go
 create mode 100644 week_1/exercise-2-2-server.go

diff --git a/week_1/exercise-2-2-client.go b/week_1/exercise-2-2-client.go
new file mode 100644
index 0000000..52e3392
--- /dev/null
+++ b/week_1/exercise-2-2-client.go
@@ -0,0 +1,52 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"net"
+	"os"
+	"strings"
+)
+
+// Declare variable of type net.Conn, called conn.
+var conn net.Conn
+
+func send(conn net.Conn, reader *bufio.Reader) {
+	for {
+		fmt.Print("> ")
+		text, _ := reader.ReadString('\n')
+		if text == "quit\n" { return }
+		fmt.Fprintf(conn, text)
+	}
+}
+
+func receive(conn net.Conn) {
+	for {
+		msg, err := bufio.NewReader(conn).ReadString('\n')
+		if err != nil { return }
+		fmt.Println("From server: " + msg)
+		fmt.Print("> ")
+	}
+}
+
+
+func main() {
+
+	reader := bufio.NewReader(os.Stdin)
+	fmt.Println("Please provide IP address and port number in the format <ip>:<port>")
+	fmt.Print("> ")
+	ipAndPort, err := reader.ReadString('\n')
+
+	fmt.Println("Debug: " + ipAndPort)
+	if err != nil { return }
+	
+	// Attempt to connect to provided ipAndPort.
+	conn, _ = net.Dial("tcp", strings.TrimSpace(ipAndPort))
+	defer conn.Close()
+
+	go send(conn, reader)
+	go receive(conn)
+
+	for {}
+
+}
diff --git a/week_1/exercise-2-2-server.go b/week_1/exercise-2-2-server.go
new file mode 100644
index 0000000..8a589a6
--- /dev/null
+++ b/week_1/exercise-2-2-server.go
@@ -0,0 +1,85 @@
+package main
+
+import (
+	"net"
+	"fmt"
+	"bufio"
+	"strings"
+	"os"
+	"strconv"
+	
+)
+
+type Connections struct {
+	m map[string]net.Conn
+}
+
+func (conns *Connections) Set(key string, val net.Conn) {
+	conns.m[key] = val
+}
+
+func MakeConns() *Connections {
+	conns := new(Connections)
+	conns.m = make(map[string]net.Conn)
+	return conns
+}
+
+func PrintHostNames() {
+	// _ is convention for throwing the return value away
+	name, _ := os.Hostname()
+	addrs, _ := net.LookupHost(name)
+	fmt.Println("Name: " + name)
+
+	for indx, addr := range addrs {
+		fmt.Println("Address number " + strconv.Itoa(indx) + ": " + addr)
+	}
+}
+
+func HandleConnection(conn net.Conn, outputs chan string, conns *Connections) {
+	defer conn.Close()
+	
+	otherEnd := conn.RemoteAddr().String()
+
+	conns.Set(otherEnd, conn)
+	
+	for {
+		msg, err := bufio.NewReader(conn).ReadString('\n')
+		if err != nil {
+			fmt.Println("Ending session with " + otherEnd)
+			delete(conns.m, otherEnd)
+			return
+		} else {
+			fmt.Print("From " + otherEnd + ": ", string(msg))
+			msgString := fmt.Sprintf("%s : %s", otherEnd, string(msg))
+			outputs <- msgString
+		}
+	}
+}
+
+func Broadcast(c chan string, conns *Connections) {
+	for {
+		msg := <- c
+		titlemsg := strings.Title(msg)
+		for k := range conns.m {
+			conns.m[k].Write([]byte(titlemsg))
+			fmt.Printf("Sending %s to %s\n", strings.TrimSpace(msg), k)
+		}
+	}
+
+}
+
+func main() {
+	PrintHostNames()
+	var conns = MakeConns()
+	outbound := make(chan string)
+	go Broadcast(outbound, conns)
+	ln, _ := net.Listen("tcp", ":18081")
+	defer ln.Close()
+	for {
+		fmt.Println("Listening for connections on port 18081...")
+		
+		conn, _ := ln.Accept()
+		fmt.Println("Got a connection...")
+		go HandleConnection(conn, outbound, conns)
+	}
+}