unknwon/the-way-to-go_ZH_CN · error

"Dial: " + err.Error()

Error message

"Dial: " + err.Error()

What it means

Panic in the WebSocket client (section 15.11): websocket.Dial("ws://localhost:12345/websocket", "", "http://localhost/") failure aborts with panic("Dial: " + err.Error()) before the readFromServer goroutine ever starts. The message embeds the dial error, typically 'connection refused' or an origin-handshake rejection.

Source

Thrown at eBook/15.11.md:58

	}
}
```

示例 15.25 [websocket_client.go](examples/chapter_15/websocket_client.go)
```go
package main

import (
	"fmt"
	"time"
	"websocket"
)

func main() {
	ws, err := websocket.Dial("ws://localhost:12345/websocket", "",
		"http://localhost/")
	if err != nil {
		panic("Dial: " + err.Error())
	}
	go readFromServer(ws)
	time.Sleep(5e9)
    ws.Close()
}

func readFromServer(ws *websocket.Conn) {
	buf := make([]byte, 1000)
	for {
		if _, err := ws.Read(buf); err != nil {
			fmt.Printf("%s\n", err.Error())
			break
		}
	}
}
```

## 链接

View on GitHub (pinned to 7a54d34d36)

Solutions

1. Start the WebSocket server example first and confirm it is accepting on :12345 before running the client
2. Match host, port, and path exactly with the server's handler route (/websocket)
3. Use the same modern library (golang.org/x/net/websocket or gorilla/websocket) on both ends so the handshake matches
4. Retry Dial a few times with a short backoff — dev servers routinely come up a beat after their clients
5. Replace the panic with log.Fatal("Dial: ", err) for a clean, logged exit

Example fix

// before
ws, err := websocket.Dial("ws://localhost:12345/websocket", "", "http://localhost/")
if err != nil {
    panic("Dial: " + err.Error())
}

// after
ws, err := websocket.Dial("ws://localhost:12345/websocket", "", "http://localhost/")
for i := 0; err != nil && i < 3; i++ {
    time.Sleep(500 * time.Millisecond)
    ws, err = websocket.Dial("ws://localhost:12345/websocket", "", "http://localhost/")
}
if err != nil {
    log.Fatal("Dial: ", err)
}

// verify the server endpoint before the websocket handshake
if c, err := net.DialTimeout("tcp", "localhost:12345", time.Second); err != nil {
    log.Fatal("websocket server not up on localhost:12345:", err)
} else {
    c.Close()
}
ws, err := websocket.Dial("ws://localhost:12345/websocket", "", "http://localhost/")

// bounded retry instead of panic on first failure
ws, err := websocket.Dial(addr, "", origin)
for i := 0; err != nil && i < 3; i++ {
    time.Sleep(300 * time.Millisecond)
    ws, err = websocket.Dial(addr, "", origin)
}
if err != nil {
    log.Fatal("Dial: ", err)
}

When it happens

Trigger: Dial returns an error: the server example is not running or listens elsewhere (port/path mismatch), the URL scheme is not ws://, or the third argument (origin 'http://localhost/') is rejected by the endpoint's origin check.

Common situations: Starting the client before the server (connection refused); server bound to 127.0.0.1 while the client reaches for another interface; port typos between the two listings; modern websocket libraries enforcing origin policies more strictly than the old 'websocket' package

Related errors

• Error:
• "ListenAndServe: " + err.Error()
• pkg: %v
• %d is out of the int32 range
• Error:

AI-assisted analysis of unknwon/the-way-to-go_ZH_CN@7a54d34d36 (2026-08-15). Data as JSON: /api/errors/552950e64cc5ca0e. Report an issue: GitHub.