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- // Solution to part 4 of the Whispering Gophers code lab.
- //
- // This program is a combination of parts 2 and 3.
- //
- // It listens on the host and port specified by the -listen flag.
- // For each incoming connection, it launches a goroutine that reads and decodes
- // JSON-encoded messages from the connection and prints them to standard
- // output.
- // It concurrently makes a connection the host and port specified by the -dial
- // flag, reads lines from standard input, and writes JSON-encoded messages to
- // the network connection.
- //
- // You can test it by running part3 in one terminal:
- // $ part3 -listen=localhost:8000
- // Running this program in another terminal:
- // $ part4 -listen=localhost:8001 -dial=localhost:8000
- // And running part2 in another terminal:
- // $ part2 -dial=localhost:8001
- // Lines typed in the second terminal should appear as JSON objects in the
- // first terminal, and those typed at the third terminal should appear in the
- // second.
- //
- package main
- import (
- "encoding/json"
- "flag"
- "fmt"
- "log"
- "net"
- "bufio"
- "os"
- )
- var (
- listenAddr = flag.String("listen", "", "host:port to listen on")
- dialAddr = flag.String("dial", "", "host:port to dial")
- )
- type Message struct {
- Body string
- }
- func main() {
- flag.Parse()
- // TODO: Launch dial in a new goroutine, passing in *dialAddr.
- go dial(*dialAddr)
- l, err := net.Listen("tcp", *listenAddr)
- if err != nil {
- log.Fatal("Listen error: ", err)
- }
- for {
- c, err := l.Accept()
- if err != nil {
- log.Fatal("Accept error: ", err)
- }
- go serve(c)
- }
- }
- func serve(c net.Conn) {
- defer c.Close()
- d := json.NewDecoder(c)
- for {
- var m Message
- err := d.Decode(&m)
- if err != nil {
- log.Println(err)
- return
- }
- fmt.Printf("%#v\n", m)
- }
- }
- func dial(addr string) {
- // TODO: put the contents of the main function from part 2 here.
- c, err := net.Dial("tcp", addr)
- if err != nil {
- log.Fatal("Dial error: ", err)
- }
- s := bufio.NewScanner(os.Stdin)
- e := json.NewEncoder(c)
- for s.Scan() {
- m := Message{Body: s.Text()}
- err := e.Encode(m)
- if err != nil {
- log.Fatal("Encoding error: ", err)
- }
- }
- if err := s.Err(); err != nil {
- log.Fatal("Scan error: ", err)
- }
- }
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