為了練習一些基本概念，我正在編寫一個簡單的端口掃描器。然而，當嘗試實現 goroutines 時，程序會出現恐慌，并且出現分段錯誤：Scanning ports{Port:139 State:Open}{Port:135 State:Open}{Port:136 State:Closed}{Port:131 State:Closed}{Port:131 State:Open}{Port:134 State:Closed}{Port:134 State:Open}panic: runtime error: invalid memory address or nil pointer dereference[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x4eb26a]goroutine 20 [running]:main.scanPort(0x52033b, 0x3, 0x52203e, 0xf, 0x83) /home/athos/Projects/go-tutorial/scanner.go:33 +0x1eacreated by main.main /home/athos/Projects/go-tutorial/scanner.go:41 +0xf1panic: runtime error: invalid memory address or nil pointer dereference[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x4eb26a]goroutine 23 [running]:main.scanPort(0x52033b, 0x3, 0x52203e, 0xf, 0x86) /home/athos/Projects/go-tutorial/scanner.go:33 +0x1eacreated by main.main /home/athos/Projects/go-tutorial/scanner.go:41 +0xf1exit status 2這是我的代碼：package mainimport ( "fmt" "net" "strconv" "sync" "time")var wg sync.WaitGrouptype scanResult struct { Port int State string}func scanPort(protocol, hostname string, port int) { defer wg.Done() result := scanResult{Port: port} socket := hostname + ":" + strconv.Itoa(port) conn, err := net.DialTimeout(protocol, socket, 2*time.Second) if err != nil { result.State = "Closed" fmt.Printf("%+v\n", result) } result.State = "Open" fmt.Printf("%+v\n", result) // Defers: FILO data structure defer conn.Close()}func main() { fmt.Println("Scanning ports") for i := 130; i <= 145; i++ { wg.Add(1) go scanPort("tcp", "192.168.200.103", i) } // Wait for goroutines to complete wg.Wait()}誰能幫我看看我做錯了什么？
1 回答
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TA貢獻1836條經驗 獲得超13個贊
net.DialTimeout()返回連接和錯誤，您正確檢查錯誤是否不是nil，但即使有錯誤，您只需打印并繼續。
如果存在非nil錯誤，則不應（絕不能）使用返回的連接，因為它可能是nil無效值。如果有錯誤，檢查/打印并返回，不要嘗試使用conn.
所以簡單地返回：
if err != nil {
result.State = "Closed"
fmt.Printf("%+v\n", result)
return
}
此外，如果沒有錯誤，您可以“安排”立即關閉連接，延遲。defer如果您在函數中關閉連接的最后一件事，則使用毫無意義。
所以它應該是這樣的：
conn, err := net.DialTimeout(protocol, socket, 2*time.Second)
if err != nil {
result.State = "Closed"
fmt.Printf("%+v\n", result)
return
}
defer conn.Close()
result.State = "Open"
fmt.Printf("%+v\n", result)
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