// Copyright 2015 The Gorilla WebSocket Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. package main import ( "bufio" "flag" "io" "log" "net/http" "os" "os/exec" "time" "github.com/gorilla/websocket" ) var ( addr = flag.String("addr", "127.0.0.1:8080", "http service address") cmdPath string ) const ( // Time allowed to write a message to the peer. writeWait = 10 * time.Second // Maximum message size allowed from peer. maxMessageSize = 8192 // Time allowed to read the next pong message from the peer. pongWait = 60 * time.Second // Send pings to peer with this period. Must be less than pongWait. pingPeriod = (pongWait * 9) / 10 // Time to wait before force close on connection. closeGracePeriod = 10 * time.Second ) func pumpStdin(ws *websocket.Conn, w io.Writer) { defer ws.Close() ws.SetReadLimit(maxMessageSize) ws.SetReadDeadline(time.Now().Add(pongWait)) ws.SetPongHandler(func(string) error { ws.SetReadDeadline(time.Now().Add(pongWait)); return nil }) for { _, message, err := ws.ReadMessage() if err != nil { break } message = append(message, '\n') if _, err := w.Write(message); err != nil { break } } } func pumpStdout(ws *websocket.Conn, r io.Reader, done chan struct{}) { defer func() { }() s := bufio.NewScanner(r) for s.Scan() { ws.SetWriteDeadline(time.Now().Add(writeWait)) if err := ws.WriteMessage(websocket.TextMessage, s.Bytes()); err != nil { ws.Close() break } } if s.Err() != nil { log.Println("scan:", s.Err()) } close(done) ws.SetWriteDeadline(time.Now().Add(writeWait)) ws.WriteMessage(websocket.CloseMessage, websocket.FormatCloseMessage(websocket.CloseNormalClosure, "")) time.Sleep(closeGracePeriod) ws.Close() } func ping(ws *websocket.Conn, done chan struct{}) { ticker := time.NewTicker(pingPeriod) defer ticker.Stop() for { select { case <-ticker.C: if err := ws.WriteControl(websocket.PingMessage, []byte{}, time.Now().Add(writeWait)); err != nil { log.Println("ping:", err) } case <-done: return } } } func internalError(ws *websocket.Conn, msg string, err error) { log.Println(msg, err) ws.WriteMessage(websocket.TextMessage, []byte("Internal server error.")) } var upgrader = websocket.Upgrader{} func serveWs(w http.ResponseWriter, r *http.Request) { ws, err := upgrader.Upgrade(w, r, nil) if err != nil { log.Println("upgrade:", err) return } defer ws.Close() outr, outw, err := os.Pipe() if err != nil { internalError(ws, "stdout:", err) return } defer outr.Close() defer outw.Close() inr, inw, err := os.Pipe() if err != nil { internalError(ws, "stdin:", err) return } defer inr.Close() defer inw.Close() proc, err := os.StartProcess(cmdPath, flag.Args(), &os.ProcAttr{ Files: []*os.File{inr, outw, outw}, }) if err != nil { internalError(ws, "start:", err) return } inr.Close() outw.Close() stdoutDone := make(chan struct{}) go pumpStdout(ws, outr, stdoutDone) go ping(ws, stdoutDone) pumpStdin(ws, inw) // Some commands will exit when stdin is closed. inw.Close() // Other commands need a bonk on the head. if err := proc.Signal(os.Interrupt); err != nil { log.Println("inter:", err) } select { case <-stdoutDone: case <-time.After(time.Second): // A bigger bonk on the head. if err := proc.Signal(os.Kill); err != nil { log.Println("term:", err) } <-stdoutDone } if _, err := proc.Wait(); err != nil { log.Println("wait:", err) } } func serveHome(w http.ResponseWriter, r *http.Request) { if r.URL.Path != "/" { http.Error(w, "Not found", http.StatusNotFound) return } if r.Method != http.MethodGet { http.Error(w, "Method not allowed", http.StatusMethodNotAllowed) return } http.ServeFile(w, r, "home.html") } func main() { flag.Parse() if len(flag.Args()) < 1 { log.Fatal("must specify at least one argument") } var err error cmdPath, err = exec.LookPath(flag.Args()[0]) if err != nil { log.Fatal(err) } http.HandleFunc("/", serveHome) http.HandleFunc("/ws", serveWs) server := &http.Server{ Addr: *addr, ReadHeaderTimeout: 3 * time.Second, } log.Fatal(server.ListenAndServe()) }