115 lines
2.4 KiB
Go
115 lines
2.4 KiB
Go
// Solution to part 5 of the Whispering Gophers code lab.
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//
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// This program extends part 4.
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//
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// It listens on an available public IP and port, and for each incoming
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// connection it decodes JSON-encoded messages and writes them to standard
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// output.
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// It simultaneously makes a connection to the host and port specified by -peer,
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// reads lines from standard input, and writes JSON-encoded messages to the
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// network connection.
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// The messages include the listen address. For example:
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// {"Addr": "127.0.0.1:41232", "Body": "Hello"!}
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//
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// You can test this program by listening with the dump program:
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// $ dump -listen=localhost:8000
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// In another terminal, running this program:
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// $ part5 -peer=localhost:8000
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// And in a third terminal, running part2 with the address printed by part5:
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// $ part2 -dial=192.168.1.200:54312
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// Lines typed in the third terminal should appear in the second, and those
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// typed in the second window should appear in the first.
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//
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package main
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import (
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"bufio"
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"encoding/json"
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"flag"
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"fmt"
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"log"
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"net"
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"os"
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"code.osinet.fr/fgm/whispering_gophers/util"
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)
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var (
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listenAddr = flag.String("listen", "", "peer host:port")
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peerAddr = flag.String("peer", "", "peer host:port")
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self string
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)
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type Message struct {
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Addr string
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Body string
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}
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func main() {
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flag.Parse()
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var l net.Listener
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var err error
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// Create a new listener using util.Listen and put it in a variable named l.
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if *listenAddr == "" {
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l, err = util.ListenOnFirstUsableInterface()
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} else {
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l, err = net.Listen("tcp4", *listenAddr)
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}
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if err != nil {
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log.Fatal(err)
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}
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// Set the global variable self with the address of the listener.
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self = l.Addr().String()
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// Print the address to the standard output
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fmt.Printf("Listening on %s\", ", self)
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go dial(*peerAddr)
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for {
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c, err := l.Accept()
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if err != nil {
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log.Fatal(err)
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}
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go serve(c)
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}
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}
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func serve(c net.Conn) {
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defer c.Close()
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d := json.NewDecoder(c)
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for {
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var m Message
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err := d.Decode(&m)
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if err != nil {
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log.Println(err)
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return
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}
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fmt.Printf("%#v\n", m)
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}
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}
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func dial(addr string) {
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c, err := net.Dial("tcp", addr)
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if err != nil {
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log.Fatal(err)
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}
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s := bufio.NewScanner(os.Stdin)
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e := json.NewEncoder(c)
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for s.Scan() {
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m := Message{
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// Put the self variable in the new Addr field.
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Addr: self,
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Body: s.Text(),
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}
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err := e.Encode(m)
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if err != nil {
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log.Fatal(err)
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}
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}
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if err := s.Err(); err != nil {
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log.Fatal(err)
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}
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os.Exit(0)
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}
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