I have a small TCP server running where a user can connect via telnet. There is a "menu" option loop (e.g. triggered single char input), and selecting the "L" option allows the connected user to "leave a message."
However:
I suspect I've got looping problems, but I'm at a loss to where it's breaking down.
Any ideas?
package main
import (
"bytes"
"fmt"
"log"
"net"
)
const (
port = "5555"
)
var arr []string
type Client struct {
c net.Conn
dataType string
menuCurr string
}
func NewClient() *Client {
return &(Client{})
}
func waitForInput(didInput chan<- bool) {
// Wait for a valid input here
didInput <- true
}
func main() {
log.Printf("Hello Server!")
service := ":5555"
tcpAddr, error := net.ResolveTCPAddr("tcp", service)
if error != nil {
log.Printf("Error: Could not resolve address")
} else {
netListen, error := net.Listen(tcpAddr.Network(), tcpAddr.String())
if error != nil {
log.Fatal(error)
} else {
defer netListen.Close()
for {
log.Printf("Waiting for clients")
conn, error := netListen.Accept()
if error != nil {
log.Print("Client error: ", error)
} else {
log.Printf("Client connected %s -> %s \n", conn.RemoteAddr(), conn.LocalAddr())
go handler(conn)
}
}
}
}
}
func removeClient(conn net.Conn) {
log.Printf("Client %s disconnected", conn.RemoteAddr())
conn.Close()
}
func handler(conn net.Conn) {
defer removeClient(conn)
errorChan := make(chan error)
dataChan := make(chan []byte)
// Set defaults for incoming connections
var s *Client
s = NewClient()
s.c = conn
s.dataType = "key"
s.menuCurr = "connect" // first menu every user sees
go readWrapper(conn, dataChan, errorChan)
r := bytes.NewBuffer(make([]byte, 0, 1024))
// default menu
fmt.Fprintf(conn, "Select an option:\r\n\n[L] Leave Message\r\n[!] Disconnect\r\n\nCmd? ")
for {
select {
case data := <-dataChan:
if s.menuCurr == "connect" {
fmt.Fprintf(conn, "Select an option:\r\n\n[L] Leave Message\r\n[!] Disconnect\r\n\nCmd? ")
}
if s.menuCurr == "message" {
fmt.Fprintf(conn, "Type a mesage. Escape to quit. \r\n\n")
}
// "key" responds to single character input
if s.dataType == "key" {
switch string(data) {
default:
fmt.Println("client hit invalid key...")
continue
case "L", "l":
s.dataType = "text"
s.menuCurr = "message"
continue
case "!":
fmt.Fprintf(conn, " Bye!")
fmt.Println("client chose to exit...")
break
}
}
// "Text" allows for free typing
if s.dataType == "text" {
for {
select {
case data := <-dataChan:
fmt.Fprintf(conn, string(data))
if bytes.Equal(data, []byte("\r\n")) || bytes.Equal(data, []byte("\r")) {
fmt.Fprintf(conn, "you typed: %q\r\n", r.String())
r.Reset()
s.dataType = "key"
s.menuCurr = "connect"
break
}
if bytes.Equal(data, []byte("\033")) {
fmt.Fprintf(conn, "\r\nAborted!\r\n")
r.Reset()
s.dataType = "key"
s.menuCurr = "connect"
break
}
r.Write(data)
}
log.Printf("Client %s sent: %q", conn.RemoteAddr(), string(data))
if s.menuCurr == "connect" {
break
}
}
continue
}
case err := <-errorChan:
log.Println("An error occured:", err.Error())
return
}
conn.Close()
}
}
func readWrapper(conn net.Conn, dataChan chan []byte, errorChan chan error) {
for {
buf := make([]byte, 1024)
reqLen, err := conn.Read(buf)
if err != nil {
errorChan <- err
return
}
dataChan <- buf[:reqLen]
}
}
So you almost got it!
Here is is what i was able to get working. My telnet client doesn't send until I hit return (i am on windows why \r\n instead of just \n) so i needed to strip those extra characters.
package main
import (
"bytes"
"fmt"
"log"
"net"
"strings"
)
const (
port = "5555"
)
var arr []string
type Client struct {
c net.Conn
dataType string
menuCurr string
}
func NewClient() *Client {
return &(Client{})
}
func waitForInput(didInput chan<- bool) {
// Wait for a valid input here
didInput <- true
}
func main() {
log.Printf("Hello Server!")
service := ":5555"
tcpAddr, error := net.ResolveTCPAddr("tcp", service)
if error != nil {
log.Printf("Error: Could not resolve address")
} else {
netListen, error := net.Listen(tcpAddr.Network(), tcpAddr.String())
if error != nil {
log.Fatal(error)
} else {
defer netListen.Close()
for {
log.Printf("Waiting for clients")
conn, error := netListen.Accept()
if error != nil {
log.Print("Client error: ", error)
} else {
log.Printf("Client connected %s -> %s \n", conn.RemoteAddr(), conn.LocalAddr())
go handler(conn)
}
}
}
}
}
func removeClient(conn net.Conn) {
log.Printf("Client %s disconnected", conn.RemoteAddr())
conn.Close()
}
func handler(conn net.Conn) {
defer removeClient(conn)
errorChan := make(chan error)
dataChan := make(chan []byte)
// Set defaults for incoming connections
var s *Client
s = NewClient()
s.c = conn
s.dataType = "key"
s.menuCurr = "connect" // first menu every user sees
go readWrapper(conn, dataChan, errorChan)
r := bytes.NewBuffer(make([]byte, 0, 1024))
// default menu
fmt.Fprintf(conn, "Select an option:\r\n\n[L] Leave Message\r\n[!] Disconnect\r\n\nCmd? ")
for {
select {
case data := <-dataChan:
// notice how i removed the current menu state
// "key" responds to single character input
if s.dataType == "key" {
t := strings.TrimSuffix(strings.TrimSuffix(string(data), "\r\n"), "\n")
switch t {
default:
fmt.Println("client hit invalid key...")
// remove the continue since the menu prints at the bottom
// continue
case "L", "l":
s.dataType = "text"
s.menuCurr = "message"
// notice the message here and the break instead of the continue.
// if we use continue instead it will wait until your user sends something
// with a break instead it will fall through and start collecting the text
fmt.Fprintf(conn, "Type a mesage. Escape to quit. \r\n\n")
break
case "!":
fmt.Fprintf(conn, " Bye!")
fmt.Println("client chose to exit...")
// tell current menu to exit
s.menuCurr = "exit"
}
}
// "Text" allows for free typing
if s.dataType == "text" {
for {
select {
case data := <-dataChan:
fmt.Fprintf(conn, string(data))
if bytes.Equal(data, []byte("\r\n")) || bytes.Equal(data, []byte("\r")) {
fmt.Fprintf(conn, "you typed: %q\r\n", r.String())
r.Reset()
s.dataType = "key"
s.menuCurr = "connect"
break
}
if bytes.Equal(data, []byte("\033")) || bytes.Equal(data, []byte("\033\r\n")) {
fmt.Fprintf(conn, "\r\nAborted!\r\n")
r.Reset()
s.dataType = "key"
s.menuCurr = "connect"
break
}
r.Write(data)
}
log.Printf("Client %s sent: %q", conn.RemoteAddr(), r.String())
if s.menuCurr == "connect" {
break
}
}
}
if s.menuCurr == "connect" {
fmt.Fprintf(conn, "Select an option:\r\n\n[L] Leave Message\r\n[!] Disconnect\r\n\nCmd? ")
}
// fall through statement to close connection
if s.menuCurr == "exit" {
break
}
// otherwise continue printing menu for invalid submissions
continue
case err := <-errorChan:
log.Println("An error occured:", err.Error())
return
}
fmt.Println("closing")
break
}
conn.Close()
}
func readWrapper(conn net.Conn, dataChan chan []byte, errorChan chan error) {
for {
buf := make([]byte, 1024)
reqLen, err := conn.Read(buf)
if err != nil {
errorChan <- err
return
}
dataChan <- buf[:reqLen]
}
}