GO语言练习:网络编程 ICMP 示例

 1 package main
 2 
 3 import (
 4 "fmt"
 5 "net"
 6 "os"
 7 "io"
 8 "bytes"
 9 )
10 
11 func main() {
12 if len(os.Args) != 2 {
13 fmt.Println("Usage : ", os.Args[0], "host")
14 os.Exit(0)
15  }
16 service := os.Args[1]
17 
18 conn, err := net.Dial("ip4:icmp", service)
19  checkError(err)
20 
21 var msg [512]byte
22 msg[0] = 8
23 msg[1] = 0
24 msg[2] = 0
25 msg[3] = 0
26 msg[4] = 0
27 msg[5] = 13
28 msg[6] = 0
29 msg[7] = 37
30 len := 8
31 check := checkSum(msg[0:len])
32 msg[2] = byte(check >> 8)
33 msg[3] = byte(check & 255)
34 
35 _, err = conn.Write(msg[0:len])
36  checkError(err)
37 
38 fmt.Println("Got response")
39 if msg[5] == 13 {
40 fmt.Println("Identifier matches")
41  }
42 if msg[7] == 37 {
43 fmt.Println("Sequence matches")
44  }
45 
46 os.Exit(0)
47 }
48 
49 func checkSum(msg []byte) uint16 {
50 sum := 0
51 
52 for n := 1; n < len(msg) - 1; n += 2 {
53 sum += int(msg[n]) * 256 + int(msg[n+1])
54  }
55 sum = (sum >> 16 ) + (sum & 0xffff)
56 sum += (sum >> 16)
57 var answer uint16 = uint16(^sum)
58 return answer
59 }
60 
61 func checkError(err error) {
62 if err != nil {
63 fmt.Fprintf(os.Stderr, "Fatal error : %s\n", err.Error())
64 os.Exit(1)
65  }
66 }
67 
68 func readFully(conn net.Conn) ([]byte, error) {
69  defer conn.Close()
70 
71 result := bytes.NewBuffer(nil)
72 var buf [512]byte
73 for {
74 n, err := conn.Read(buf[0:])
75 result.Write(buf[0:n])
76 if err != nil {
77 if err == io.EOF {
78 break
79  }
80 return nil, err
81  }
82  }
83 
84 return result.Bytes(), nil
85 }

$ go build icmptest.go 
$ ls
icmptest icmptest.go
$ ./icmptest www.baidu.com
Got response
Identifier matches
Sequence matches

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