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