為了練習(xí)一些基本概念，我正在編寫一個(gè)簡(jiǎn)單的端口掃描器。然而，當(dāng)嘗試實(shí)現(xiàn) goroutines 時(shí)，程序會(huì)出現(xiàn)恐慌，并且出現(xiàn)分段錯(cuò)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(shuí)能幫我看看我做錯(cuò)了什么？
1 回答
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net.DialTimeout()返回連接和錯(cuò)誤，您正確檢查錯(cuò)誤是否不是nil，但即使有錯(cuò)誤，您只需打印并繼續(xù)。
如果存在非nil錯(cuò)誤，則不應(yīng)（絕不能）使用返回的連接，因?yàn)樗赡苁莕il無(wú)效值。如果有錯(cuò)誤，檢查/打印并返回，不要嘗試使用conn.
所以簡(jiǎn)單地返回：
if err != nil {
result.State = "Closed"
fmt.Printf("%+v\n", result)
return
}
此外，如果沒有錯(cuò)誤，您可以“安排”立即關(guān)閉連接，延遲。defer如果您在函數(shù)中關(guān)閉連接的最后一件事，則使用毫無(wú)意義。
所以它應(yīng)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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