chat.go/chatserver.go

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package main
// Lot's of learning right out of the gate:
// https://stackoverflow.com/questions/51472020/how-to-get-the-size-of-available-tcp-data
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import (
"bufio"
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"flag"
"fmt"
"io"
"net"
"os"
"strconv"
"sync"
"time"
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)
type bufferedConn struct {
r *bufio.Reader
rout io.Reader
net.Conn
}
func newBufferedConn(c net.Conn) bufferedConn {
return bufferedConn{bufio.NewReader(c), nil, c}
}
func (b bufferedConn) Peek(n int) ([]byte, error) {
return b.r.Peek(n)
}
func (b bufferedConn) Buffered() (int) {
return b.r.Buffered()
}
func (b bufferedConn) Read(p []byte) (int, error) {
if b.rout != nil {
return b.rout.Read(p)
}
return b.r.Read(p)
}
type myMsg struct {
sender net.Conn
bytes []byte
receivedAt time.Time
}
var firstMsgs chan myMsg
var myMsgs chan myMsg
var myUnsortedConns map[net.Conn]bool
var myRawConns map[net.Conn]bool
var newConns chan net.Conn
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func usage() {
fmt.Fprintf(os.Stderr, "\nusage: go run chatserver.go\n")
flag.PrintDefaults();
fmt.Println()
os.Exit(1)
}
func handleRaw(conn bufferedConn) {
// Handle all subsequent packets
buf := make([]byte, 1024)
for {
fmt.Fprintf(os.Stdout, "[raw] Waiting for message...\n");
count, err := conn.Read(buf)
if nil != err {
if io.EOF != err {
fmt.Fprintf(os.Stderr, "Non-EOF socket error: %s\n", err)
}
fmt.Fprintf(os.Stdout, "Ending socket\n")
break
}
// Fun fact: if the buffer's current length (not capacity) is 0
// then the Read returns 0 without error
if 0 == count {
fmt.Fprintf(os.Stdout, "Weird")
continue
}
fmt.Fprintf(os.Stdout, "Queing message...\n");
myMsgs <- myMsg{
receivedAt: time.Now(),
sender: conn,
bytes: buf[0:count],
}
}
}
func handleSorted(conn bufferedConn) {
// at this piont we've already at least one byte via Peek()
// so the first packet is available in the buffer
n := conn.Buffered()
firstMsg, err := conn.Peek(n)
if nil != err {
panic(err)
}
firstMsgs <- myMsg{
receivedAt: time.Now(),
sender: conn,
bytes: firstMsg,
}
// TODO
// * TCP-CHAT
// * HTTP
// * TLS
// Handle all subsequent packets
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buf := make([]byte, 1024)
for {
fmt.Fprintf(os.Stdout, "[sortable] Waiting for message...\n");
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count, err := conn.Read(buf)
if nil != err {
if io.EOF != err {
fmt.Fprintf(os.Stderr, "Non-EOF socket error: %s\n", err)
}
fmt.Fprintf(os.Stdout, "Ending socket\n")
break
}
// Fun fact: if the buffer's current length (not capacity) is 0
// then the Read returns 0 without error
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if 0 == count {
// fmt.Fprintf(os.Stdout, "Weird")
continue
}
myMsgs <- myMsg{
receivedAt: time.Now(),
sender: conn,
bytes: buf[0:count],
}
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}
}
// TODO https://github.com/polvi/sni
func handleConnection(conn net.Conn) {
fmt.Fprintf(os.Stdout, "Accepting socket\n")
m := sync.Mutex{}
virgin := true
myUnsortedConns[conn] = true
// Why don't these work?
//buf := make([]byte, 0, 1024)
//buf := []byte{}
// But this does
bufConn := newBufferedConn(conn)
go func() {
// Handle First Packet
fmsg, err := bufConn.Peek(1)
if nil != err {
panic(err)
}
fmt.Fprintf(os.Stdout, "[First Byte] %s\n", fmsg)
m.Lock();
if virgin {
virgin = false
go handleSorted(bufConn)
} else {
go handleRaw(bufConn)
}
m.Unlock();
}()
time.Sleep(250 * 1000000)
// If we still haven't received data from the client
// assume that the client must be expecting a welcome from us
m.Lock()
if virgin {
virgin = false
// don't block for this
// let it be handled after the unlock
defer fmt.Fprintf(conn, "Welcome! This is an open relay chat server. There is no security yet.\n")
}
m.Unlock()
}
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func main() {
firstMsgs = make(chan myMsg, 128)
myMsgs = make(chan myMsg, 128)
newConns = make(chan net.Conn, 128)
myRawConns = make(map[net.Conn]bool)
myUnsortedConns = make(map[net.Conn]bool)
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flag.Usage = usage
port:= flag.Uint("telnet-port", 4080, "tcp telnet chat port")
flag.Parse()
addr := ":" + strconv.Itoa(int(*port))
// https://golang.org/pkg/net/#Conn
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sock, err := net.Listen("tcp", addr)
if nil != err {
fmt.Fprintf(os.Stderr, "Couldn't bind to TCP socket %q: %s\n", addr, err)
os.Exit(2)
}
fmt.Println("Listening on", addr);
go func() {
for {
conn, err := sock.Accept()
if err != nil {
// Not sure what kind of error this could be or how it could happen.
// Could a connection abort or end before it's handled?
fmt.Fprintf(os.Stderr, "Error accepting connection:\n%s\n", err)
}
newConns <- conn
}
}()
for {
select {
case conn := <- newConns:
go handleConnection(conn)
case msg := <- myMsgs:
ts, err := msg.receivedAt.MarshalJSON()
if nil != err {
fmt.Fprintf(os.Stderr, "[Error] %s\n", err)
}
fmt.Fprintf(os.Stdout, "[Timestamp] %s\n", ts)
fmt.Fprintf(os.Stdout, "[Remote] %s\n", msg.sender.RemoteAddr().String())
fmt.Fprintf(os.Stdout, "[Message] %s\n", msg.bytes);
for conn, _ := range myRawConns {
if msg.sender == conn {
continue
}
// backlogged connections could prevent a next write,
// so this should be refactored into a goroutine
// And what to do about slow clients that get behind (or DoS)?
// SetDeadTime and Disconnect them?
conn.Write(msg.bytes)
}
case msg := <- firstMsgs:
fmt.Fprintf(os.Stdout, "f [First Message]\n")
ts, err := msg.receivedAt.MarshalJSON()
if nil != err {
fmt.Fprintf(os.Stderr, "f [Error] %s\n", err)
}
fmt.Fprintf(os.Stdout, "f [Timestamp] %s\n", ts)
fmt.Fprintf(os.Stdout, "f [Remote] %s\n", msg.sender.RemoteAddr().String())
fmt.Fprintf(os.Stdout, "f [Message] %s\n", msg.bytes);
}
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}
}