2018-07-22 01:52:49 +00:00
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package main
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2018-07-29 06:45:12 +00:00
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// Lot's of learning right out of the gate:
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// https://stackoverflow.com/questions/51472020/how-to-get-the-size-of-available-tcp-data
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2018-07-22 01:52:49 +00:00
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import (
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2018-07-29 06:45:12 +00:00
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"bufio"
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2018-07-22 01:52:49 +00:00
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"flag"
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"fmt"
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"io"
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"net"
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"os"
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"strconv"
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2018-07-29 06:45:12 +00:00
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"sync"
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2018-07-22 03:58:05 +00:00
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"time"
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2018-07-22 01:52:49 +00:00
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)
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2018-07-29 06:45:12 +00:00
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type bufferedConn struct {
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r *bufio.Reader
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rout io.Reader
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net.Conn
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}
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func newBufferedConn(c net.Conn) bufferedConn {
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return bufferedConn{bufio.NewReader(c), nil, c}
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}
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func (b bufferedConn) Peek(n int) ([]byte, error) {
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return b.r.Peek(n)
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}
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func (b bufferedConn) Buffered() (int) {
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return b.r.Buffered()
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}
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func (b bufferedConn) Read(p []byte) (int, error) {
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if b.rout != nil {
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return b.rout.Read(p)
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}
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return b.r.Read(p)
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}
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2018-07-22 03:58:05 +00:00
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type myMsg struct {
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sender net.Conn
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bytes []byte
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receivedAt time.Time
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}
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var firstMsgs chan myMsg
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var myMsgs chan myMsg
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var myUnsortedConns map[net.Conn]bool
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var myRawConns map[net.Conn]bool
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var newConns chan net.Conn
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2018-07-22 01:52:49 +00:00
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func usage() {
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fmt.Fprintf(os.Stderr, "\nusage: go run chatserver.go\n")
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flag.PrintDefaults();
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fmt.Println()
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os.Exit(1)
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}
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2018-07-29 06:45:12 +00:00
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func handleRaw(conn bufferedConn) {
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// Handle all subsequent packets
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buf := make([]byte, 1024)
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for {
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fmt.Fprintf(os.Stdout, "[raw] Waiting for message...\n");
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count, err := conn.Read(buf)
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if nil != err {
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if io.EOF != err {
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fmt.Fprintf(os.Stderr, "Non-EOF socket error: %s\n", err)
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}
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fmt.Fprintf(os.Stdout, "Ending socket\n")
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break
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}
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// Fun fact: if the buffer's current length (not capacity) is 0
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// then the Read returns 0 without error
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if 0 == count {
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fmt.Fprintf(os.Stdout, "Weird")
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continue
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}
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fmt.Fprintf(os.Stdout, "Queing message...\n");
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myMsgs <- myMsg{
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receivedAt: time.Now(),
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sender: conn,
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bytes: buf[0:count],
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}
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}
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}
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func handleSorted(conn bufferedConn) {
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// at this piont we've already at least one byte via Peek()
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// so the first packet is available in the buffer
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n := conn.Buffered()
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firstMsg, err := conn.Peek(n)
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if nil != err {
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panic(err)
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}
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firstMsgs <- myMsg{
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receivedAt: time.Now(),
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sender: conn,
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bytes: firstMsg,
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}
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// TODO
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// * TCP-CHAT
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// * HTTP
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// * TLS
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// Handle all subsequent packets
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buf := make([]byte, 1024)
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for {
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fmt.Fprintf(os.Stdout, "[sortable] Waiting for message...\n");
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count, err := conn.Read(buf)
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if nil != err {
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if io.EOF != err {
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fmt.Fprintf(os.Stderr, "Non-EOF socket error: %s\n", err)
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}
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fmt.Fprintf(os.Stdout, "Ending socket\n")
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break
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}
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2018-07-29 06:45:12 +00:00
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// Fun fact: if the buffer's current length (not capacity) is 0
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// then the Read returns 0 without error
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if 0 == count {
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// fmt.Fprintf(os.Stdout, "Weird")
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continue
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}
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2018-07-22 03:58:05 +00:00
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myMsgs <- myMsg{
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receivedAt: time.Now(),
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sender: conn,
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bytes: buf[0:count],
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}
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2018-07-22 01:52:49 +00:00
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}
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}
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2018-07-29 06:45:12 +00:00
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// TODO https://github.com/polvi/sni
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func handleConnection(conn net.Conn) {
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fmt.Fprintf(os.Stdout, "Accepting socket\n")
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m := sync.Mutex{}
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virgin := true
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myUnsortedConns[conn] = true
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// Why don't these work?
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//buf := make([]byte, 0, 1024)
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//buf := []byte{}
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// But this does
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bufConn := newBufferedConn(conn)
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go func() {
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// Handle First Packet
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fmsg, err := bufConn.Peek(1)
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if nil != err {
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panic(err)
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}
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fmt.Fprintf(os.Stdout, "[First Byte] %s\n", fmsg)
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m.Lock();
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if virgin {
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virgin = false
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go handleSorted(bufConn)
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} else {
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go handleRaw(bufConn)
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}
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m.Unlock();
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}()
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time.Sleep(250 * 1000000)
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// If we still haven't received data from the client
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// assume that the client must be expecting a welcome from us
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m.Lock()
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if virgin {
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virgin = false
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// don't block for this
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// let it be handled after the unlock
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defer fmt.Fprintf(conn, "Welcome! This is an open relay chat server. There is no security yet.\n")
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}
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m.Unlock()
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}
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2018-07-22 01:52:49 +00:00
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func main() {
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firstMsgs = make(chan myMsg, 128)
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myMsgs = make(chan myMsg, 128)
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newConns = make(chan net.Conn, 128)
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myRawConns = make(map[net.Conn]bool)
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myUnsortedConns = make(map[net.Conn]bool)
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flag.Usage = usage
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port:= flag.Uint("telnet-port", 4080, "tcp telnet chat port")
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flag.Parse()
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addr := ":" + strconv.Itoa(int(*port))
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2018-07-22 03:58:05 +00:00
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// https://golang.org/pkg/net/#Conn
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sock, err := net.Listen("tcp", addr)
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if nil != err {
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fmt.Fprintf(os.Stderr, "Couldn't bind to TCP socket %q: %s\n", addr, err)
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os.Exit(2)
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}
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fmt.Println("Listening on", addr);
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2018-07-22 03:58:05 +00:00
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go func() {
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for {
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2018-07-29 06:45:12 +00:00
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conn, err := sock.Accept()
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if err != nil {
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// Not sure what kind of error this could be or how it could happen.
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// Could a connection abort or end before it's handled?
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fmt.Fprintf(os.Stderr, "Error accepting connection:\n%s\n", err)
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}
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newConns <- conn
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}
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}()
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for {
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select {
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case conn := <- newConns:
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go handleConnection(conn)
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case msg := <- myMsgs:
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2018-07-22 03:58:05 +00:00
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ts, err := msg.receivedAt.MarshalJSON()
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if nil != err {
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fmt.Fprintf(os.Stderr, "[Error] %s\n", err)
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}
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fmt.Fprintf(os.Stdout, "[Timestamp] %s\n", ts)
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fmt.Fprintf(os.Stdout, "[Remote] %s\n", msg.sender.RemoteAddr().String())
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fmt.Fprintf(os.Stdout, "[Message] %s\n", msg.bytes);
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for conn, _ := range myRawConns {
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if msg.sender == conn {
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continue
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}
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// backlogged connections could prevent a next write,
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// so this should be refactored into a goroutine
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// And what to do about slow clients that get behind (or DoS)?
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// SetDeadTime and Disconnect them?
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conn.Write(msg.bytes)
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}
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2018-07-29 06:45:12 +00:00
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case msg := <- firstMsgs:
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fmt.Fprintf(os.Stdout, "f [First Message]\n")
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ts, err := msg.receivedAt.MarshalJSON()
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if nil != err {
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fmt.Fprintf(os.Stderr, "f [Error] %s\n", err)
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}
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fmt.Fprintf(os.Stdout, "f [Timestamp] %s\n", ts)
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fmt.Fprintf(os.Stdout, "f [Remote] %s\n", msg.sender.RemoteAddr().String())
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fmt.Fprintf(os.Stdout, "f [Message] %s\n", msg.bytes);
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2018-07-22 03:58:05 +00:00
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}
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2018-07-22 01:52:49 +00:00
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}
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}
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