go标准库的学习-net

时间 2019-11-09

标签标准学习繁體版

原文原文链接

参考：https://studygolang.com/pkgdochtml

导入方式：golang

import "net"

net包提供了可移植的网络I/O接口，包括TCP/IP、UDP、域名解析和Unix域socket。网络

虽然本包提供了对网络原语的访问，大部分使用者只须要Dial、Listen和Accept函数提供的基本接口；以及相关的Conn和Listener接口。crypto/tls包提供了相同的接口和相似的Dial和Listen函数。socket

1）IPtcp

type IP

type IP []byte

IP类型是表明单个IP地址的[]byte切片。本包的函数均可以接受4字节（IPv4）和16字节（IPv6）的切片做为输入。函数

注意，IP地址是IPv4地址仍是IPv6地址是语义上的属性，而不取决于切片的长度：16字节的切片也能够是IPv4地址。oop

func IPv4

func IPv4(a, b, c, d byte) IP

IPv4返回包含一个IPv4地址a.b.c.d的IP地址（16字节格式）。ui

func ParseIP

func ParseIP(s string) IP

ParseIP将s解析为IP地址，并返回该地址。若是s不是合法的IP地址文本表示，ParseIP会返回nil。编码

字符串能够是小数点分隔的IPv4格式（如"74.125.19.99"）或IPv6格式（如"2001:4860:0:2001::68"）格式。spa

举例：

package main 
import(
    "fmt"
    "net"
    "reflect"
)

var parseIPTests = []struct {
    in  string
    out net.IP
}{
    {"127.0.1.2", net.IPv4(127, 0, 1, 2)},
    {"127.0.0.1", net.IPv4(127, 0, 0, 1)},
    {"127.001.002.003", net.IPv4(127, 1, 2, 3)},
    {"::ffff:127.1.2.3", net.IPv4(127, 1, 2, 3)},
    {"::ffff:127.001.002.003", net.IPv4(127, 1, 2, 3)},
    {"::ffff:7f01:0203", net.IPv4(127, 1, 2, 3)},
    {"0:0:0:0:0000:ffff:127.1.2.3", net.IPv4(127, 1, 2, 3)},
    {"0:0:0:0:000000:ffff:127.1.2.3", net.IPv4(127, 1, 2, 3)},
    {"0:0:0:0::ffff:127.1.2.3", net.IPv4(127, 1, 2, 3)},

    {"2001:4860:0:2001::68", net.IP{0x20, 0x01, 0x48, 0x60, 0, 0, 0x20, 0x01, 0, 0, 0, 0, 0, 0, 0x00, 0x68}},
    {"2001:4860:0000:2001:0000:0000:0000:0068", net.IP{0x20, 0x01, 0x48, 0x60, 0, 0, 0x20, 0x01, 0, 0, 0, 0, 0, 0, 0x00, 0x68}},

    {"-0.0.0.0", nil},
    {"0.-1.0.0", nil},
    {"0.0.-2.0", nil},
    {"0.0.0.-3", nil},
    {"127.0.0.256", nil},
    {"abc", nil},
    {"123:", nil},
    {"fe80::1%lo0", nil},
    {"fe80::1%911", nil},
    {"", nil},
    {"a1:a2:a3:a4::b1:b2:b3:b4", nil}, // Issue 6628
}

func main() {
    for i, tt := range parseIPTests {
        if out := net.ParseIP(tt.in); !reflect.DeepEqual(out, tt.out) {//若是获得的out与上面的结构体中out的值不等的话，就返回错误
            fmt.Errorf("ParseIP(%q) = %v, want %v", tt.in, out, tt.out)
        } else{
            fmt.Printf("%v out is : %v\n", i, out)
        }
        if tt.in == "" { //若是in为空，则跳出该循环，继续下一个循环
            fmt.Println("%v is '' ")
            continue
        }
        var out net.IP 
        //解码tt.in为IP，并将值输入out，若是该out与tt.out不等，或者运行UnmarshalText出错(即无out值)但tt.out不为nil，或者运行UnmarshalText没出错(即有out值)但tt.out为nil的状况下则报错
        if err := out.UnmarshalText([]byte(tt.in)); !reflect.DeepEqual(out, tt.out) || (tt.out == nil) != (err != nil) {
            fmt.Errorf("IP.UnmarshalText(%q) = %v, %v, want %v", tt.in, out, err, tt.out)
        }else{
            fmt.Printf("%v out is : %v\n", i, out)            
        }
    }
}

userdeMBP:go-learning user$ go run test.go 127.0.0.1
0 out is : 127.0.1.2
0 out is : 127.0.1.2
1 out is : 127.0.0.1
1 out is : 127.0.0.1
2 out is : 127.1.2.3
2 out is : 127.1.2.3
3 out is : 127.1.2.3
3 out is : 127.1.2.3
4 out is : 127.1.2.3
4 out is : 127.1.2.3
5 out is : 127.1.2.3
5 out is : 127.1.2.3
6 out is : 127.1.2.3
6 out is : 127.1.2.3
7 out is : 127.1.2.3
7 out is : 127.1.2.3
8 out is : 127.1.2.3
8 out is : 127.1.2.3
9 out is : 2001:4860:0:2001::68
9 out is : 2001:4860:0:2001::68
10 out is : 2001:4860:0:2001::68
10 out is : 2001:4860:0:2001::68
11 out is : <nil>
11 out is : <nil>
12 out is : <nil>
12 out is : <nil>
13 out is : <nil>
13 out is : <nil>
14 out is : <nil>
14 out is : <nil>
15 out is : <nil>
15 out is : <nil>
16 out is : <nil>
16 out is : <nil>
17 out is : <nil>
17 out is : <nil>
18 out is : <nil>
18 out is : <nil>
19 out is : <nil>
19 out is : <nil>
20 out is : <nil>
%v is '' 
21 out is : <nil>
21 out is : <nil>

func (IP) String

func (ip IP) String() string

String返回IP地址ip的字符串表示。若是ip是IPv4地址，返回值的格式为点分隔的，如"74.125.19.99"；不然表示为IPv6格式，如"2001:4860:0:2001::68"。

举例：

package main 
import(
    "fmt" "os" "net" ) func main() { if len(os.Args) != 2{ fmt.Fprintf(os.Stderr, "Usage: %s ip-addr\n", os.Args[0]) os.Exit(1) } name := os.Args[1] addr := net.ParseIP(name) if addr == nil { fmt.Println("Invalid address") }else{ fmt.Println("the address is", addr.String()) } os.Exit(0) }

userdeMacBook-Pro:go-learning user$ go run test.go
Usage: /var/folders/2_/g5wrlg3x75zbzyqvsd5f093r0000gn/T/go-build258331112/b001/exe/test ip-addr exit status 1 userdeMacBook-Pro:go-learning user$ go run test.go 127.0.0.1 the address is 127.0.0.1

func (IP) MarshalText

func (ip IP) MarshalText() ([]byte, error)

MarshalText实现了encoding.TextMarshaler接口，返回值和String方法同样。即将ip的值编码为[]byte类型返回

func (*IP) UnmarshalText

func (ip *IP) UnmarshalText(text []byte) error

UnmarshalText实现了encoding.TextUnmarshaler接口。IP地址字符串应该是ParseIP函数能够接受的格式。即将text的值解码为IP类型而后存储到ip中

举例：

package main 
import(
    "fmt"
    "net"
    "log"
    "reflect"
)
func main() {
    for _, in := range [][]byte{[]byte("127.0.1.2"), []byte("0:0:0:0:0000:ffff:127.1.2.3")} {
        var out = net.IP{1, 2, 3, 4}
        //err应该为nil，且out应该为nil，这样才不会报错，解码in的值将写到out中
        if err := out.UnmarshalText(in); err != nil || out == net.IP{1, 2, 3, 4} {
            fmt.Errorf("UnmarshalText(%v) = %v, %v; want nil, nil", in, out, err)
        }else{
            fmt.Printf("in is : %q, out is %v\n", in, out)
        }
    }
    var ip = net.IP{1, 2, 3, 4}
    //将ip编码为[]byte类型,返回got
    got, err := ip.MarshalText()
    if err != nil {
        log.Fatal(err)
    }
    //got应该等于[]byte("")
    if !reflect.DeepEqual(got, []byte("1.2.3.4")) {
        fmt.Errorf(`got %#v, want []byte("")`, got)
    }else{
        fmt.Printf("got is : %q\n", got)
    }
}

userdeMBP:go-learning user$ go run test.go 127.0.0.1
in is : "127.0.1.2", out is 127.0.1.2
in is : "0:0:0:0:0000:ffff:127.1.2.3", out is 127.1.2.3
got is : "1.2.3.4"

func (IP) IsGlobalUnicast

func (ip IP) IsGlobalUnicast() bool

若是ip是全局单播地址，则返回真。

func (IP) IsLinkLocalUnicast

func (ip IP) IsLinkLocalUnicast() bool

若是ip是链路本地单播地址，则返回真。

func (IP) IsInterfaceLocalMulticast

func (ip IP) IsInterfaceLocalMulticast() bool

若是ip是接口本地组播地址，则返回真。

func (IP) IsLinkLocalMulticast

func (ip IP) IsLinkLocalMulticast() bool

若是ip是链路本地组播地址，则返回真。

func (IP) IsMulticast

func (ip IP) IsMulticast() bool

若是ip是组播地址，则返回真。

func (IP) IsLoopback

func (ip IP) IsLoopback() bool

若是ip是环回地址，则返回真。

func (IP) IsUnspecified

func (ip IP) IsUnspecified() bool

若是ip是未指定地址，则返回真。

func (IP) Equal

func (ip IP) Equal(x IP) bool

若是ip和x表明同一个IP地址，Equal会返回真。表明同一地址的IPv4地址和IPv6地址也被认为是相等的。

func (IP) To16

func (ip IP) To16() IP

To16将一个IP地址转换为16字节表示。若是ip不是一个IP地址（长度错误），To16会返回nil。

func (IP) To4

func (ip IP) To4() IP

To4将一个IPv4地址转换为4字节表示。若是ip不是IPv4地址，To4会返回nil。

func (IP) DefaultMask

func (ip IP) DefaultMask() IPMask

函数返回IP地址ip的默认子网掩码。只有IPv4有默认子网掩码；若是ip不是合法的IPv4地址，会返回nil。

func (IP) Mask

func (ip IP) Mask(mask IPMask) IP

Mask方法认为mask为ip的子网掩码，返回ip的网络地址部分的ip。（主机地址部分都置0）

举例：

package main 
import(
    "fmt"
    "net"
    // "log"
    // "reflect"
)

func main() {
    var ip = net.IP{127, 168, 124, 1}
    fmt.Println(ip.DefaultMask()) //ff000000,即255.0.0.0
    fmt.Printf("%q\n", ip) //"127.168.124.1"
    //将子网掩码设为255.255.0.0后，返回的ip将会符合对应的子网掩码，因此返回"127.168.0.0"
    //若是设置的是255.0.0.0，则返回"127.0.0.0"
    ip = ip.Mask(net.IPv4Mask(255, 255, 0, 0)) 
    fmt.Printf("%q\n", ip) //"127.168.0.0"
}

type ParseError

type ParseError struct {
    Type string
    Text string
}

ParseError表明一个格式错误的字符串，Type为指望的格式。

func (*ParseError) Error

func (e *ParseError) Error() string

func ParseCIDR

func ParseCIDR(s string) (IP, *IPNet, error)

ParseCIDR将s做为一个CIDR（无类型域间路由）的IP地址和掩码字符串，如"192.168.100.1/24"或"2001:DB8::/48"，解析并返回IP地址和IP网络，参见RFC 4632和RFC 4291。

本函数会返回IP地址和该IP所在的网络和掩码。例如，ParseCIDR("192.168.100.1/16")会返回IP地址192.168.100.1和IP网络192.168.0.0/16。

举例：

package main 
import(
    "fmt"
    "net"
    // "log"
    "reflect"
)

var parseCIDRTests = []struct {
    in  string
    ip  net.IP
    net *net.IPNet
    err error
}{
    {"135.104.0.0/32", net.IPv4(135, 104, 0, 0), &net.IPNet{IP: net.IPv4(135, 104, 0, 0), Mask: net.IPv4Mask(255, 255, 255, 255)}, nil},
    {"0.0.0.0/24", net.IPv4(0, 0, 0, 0), &net.IPNet{IP: net.IPv4(0, 0, 0, 0), Mask: net.IPv4Mask(255, 255, 255, 0)}, nil},
    {"135.104.0.1/24", net.IPv4(135, 104, 0, 1), &net.IPNet{IP: net.IPv4(135, 104, 0, 0), Mask: net.IPv4Mask(255, 255, 255, 0)}, nil},
    {"::1/128", net.ParseIP("::1"), &net.IPNet{IP: net.ParseIP("::1"), Mask: net.IPMask(net.ParseIP("ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff"))}, nil},
    {"abcd:2345::/127", net.ParseIP("abcd:2345::"), &net.IPNet{IP: net.ParseIP("abcd:2345::"), Mask: net.IPMask(net.ParseIP("ffff:ffff:ffff:ffff:ffff:ffff:ffff:fffe"))}, nil},
    {"abcd:2345::/65", net.ParseIP("abcd:2345::"), &net.IPNet{IP: net.ParseIP("abcd:2345::"), Mask: net.IPMask(net.ParseIP("ffff:ffff:ffff:ffff:8000::"))}, nil},
    {"abcd:2345::/64", net.ParseIP("abcd:2345::"), &net.IPNet{IP: net.ParseIP("abcd:2345::"), Mask: net.IPMask(net.ParseIP("ffff:ffff:ffff:ffff::"))}, nil},
    {"abcd:2345::/63", net.ParseIP("abcd:2345::"), &net.IPNet{IP: net.ParseIP("abcd:2345::"), Mask: net.IPMask(net.ParseIP("ffff:ffff:ffff:fffe::"))}, nil},
    {"abcd:2345::/33", net.ParseIP("abcd:2345::"), &net.IPNet{IP: net.ParseIP("abcd:2345::"), Mask: net.IPMask(net.ParseIP("ffff:ffff:8000::"))}, nil},
    {"abcd:2345::/32", net.ParseIP("abcd:2345::"), &net.IPNet{IP: net.ParseIP("abcd:2345::"), Mask: net.IPMask(net.ParseIP("ffff:ffff::"))}, nil},
    {"abcd:2344::/31", net.ParseIP("abcd:2344::"), &net.IPNet{IP: net.ParseIP("abcd:2344::"), Mask: net.IPMask(net.ParseIP("ffff:fffe::"))}, nil},
    {"abcd:2300::/24", net.ParseIP("abcd:2300::"), &net.IPNet{IP: net.ParseIP("abcd:2300::"), Mask: net.IPMask(net.ParseIP("ffff:ff00::"))}, nil},
    {"abcd:2345::/24", net.ParseIP("abcd:2345::"), &net.IPNet{IP: net.ParseIP("abcd:2300::"), Mask: net.IPMask(net.ParseIP("ffff:ff00::"))}, nil},
    {"2001:DB8::/48", net.ParseIP("2001:DB8::"), &net.IPNet{IP: net.ParseIP("2001:DB8::"), Mask: net.IPMask(net.ParseIP("ffff:ffff:ffff::"))}, nil},
    {"2001:DB8::1/48", net.ParseIP("2001:DB8::1"), &net.IPNet{IP: net.ParseIP("2001:DB8::"), Mask: net.IPMask(net.ParseIP("ffff:ffff:ffff::"))}, nil},
    {"192.168.1.1/255.255.255.0", nil, nil, &net.ParseError{Type: "CIDR address", Text: "192.168.1.1/255.255.255.0"}},
    {"192.168.1.1/35", nil, nil, &net.ParseError{Type: "CIDR address", Text: "192.168.1.1/35"}},
    {"2001:db8::1/-1", nil, nil, &net.ParseError{Type: "CIDR address", Text: "2001:db8::1/-1"}},
    {"-0.0.0.0/32", nil, nil, &net.ParseError{Type: "CIDR address", Text: "-0.0.0.0/32"}},
    {"0.0.0.-3/32", nil, nil, &net.ParseError{Type: "CIDR address", Text: "0.0.0.-3/32"}},
    {"0.0.0.0/-0", nil, nil, &net.ParseError{Type: "CIDR address", Text: "0.0.0.0/-0"}},
    {"", nil, nil, &net.ParseError{Type: "CIDR address", Text: ""}},
}

func main() {
    for i, tt := range parseCIDRTests {
        ip, net, err := net.ParseCIDR(tt.in)
        //若是返回的err不是nil或者自定义的net.ParseError，那么将报错
        if !reflect.DeepEqual(err, tt.err) {
            fmt.Errorf("ParseCIDR(%q) = %v, %v; want %v, %v", tt.in, ip, net, tt.ip, tt.net)
        }
        //ParseCIDR没出错，且返回的ip,net和给出的值都相等则成功，不然报错
        if err == nil{
            if !tt.ip.Equal(ip) || !tt.net.IP.Equal(net.IP) || !reflect.DeepEqual(net.Mask, tt.net.Mask) {
                fmt.Errorf("ParseCIDR(%q) = %v, {%v, %v}; want %v, {%v, %v}", tt.in, ip, net.IP, net.Mask, tt.ip, tt.net.IP, tt.net.Mask)
            }else{
                fmt.Printf("%v ParseCIDR(%q) = %v, {%v, %q}\n", i, tt.in, ip, net.IP, net.Mask)
            }            
        }

    }
}

userdeMBP:go-learning user$ go run test.go
0 ParseCIDR("135.104.0.0/32") = 135.104.0.0, {135.104.0.0, "ffffffff"}
1 ParseCIDR("0.0.0.0/24") = 0.0.0.0, {0.0.0.0, "ffffff00"}
2 ParseCIDR("135.104.0.1/24") = 135.104.0.1, {135.104.0.0, "ffffff00"}
3 ParseCIDR("::1/128") = ::1, {::1, "ffffffffffffffffffffffffffffffff"}
4 ParseCIDR("abcd:2345::/127") = abcd:2345::, {abcd:2345::, "fffffffffffffffffffffffffffffffe"}
5 ParseCIDR("abcd:2345::/65") = abcd:2345::, {abcd:2345::, "ffffffffffffffff8000000000000000"}
6 ParseCIDR("abcd:2345::/64") = abcd:2345::, {abcd:2345::, "ffffffffffffffff0000000000000000"}
7 ParseCIDR("abcd:2345::/63") = abcd:2345::, {abcd:2345::, "fffffffffffffffe0000000000000000"}
8 ParseCIDR("abcd:2345::/33") = abcd:2345::, {abcd:2345::, "ffffffff800000000000000000000000"}
9 ParseCIDR("abcd:2345::/32") = abcd:2345::, {abcd:2345::, "ffffffff000000000000000000000000"}
10 ParseCIDR("abcd:2344::/31") = abcd:2344::, {abcd:2344::, "fffffffe000000000000000000000000"}
11 ParseCIDR("abcd:2300::/24") = abcd:2300::, {abcd:2300::, "ffffff00000000000000000000000000"}
12 ParseCIDR("abcd:2345::/24") = abcd:2345::, {abcd:2300::, "ffffff00000000000000000000000000"}
13 ParseCIDR("2001:DB8::/48") = 2001:db8::, {2001:db8::, "ffffffffffff00000000000000000000"}
14 ParseCIDR("2001:DB8::1/48") = 2001:db8::1, {2001:db8::, "ffffffffffff00000000000000000000"}

type IPMask

type IPMask []byte

IPMask表明一个IP地址的掩码。

func IPv4Mask

func IPv4Mask(a, b, c, d byte) IPMask

IPv4Mask返回一个4字节格式的IPv4掩码a.b.c.d。

func CIDRMask

func CIDRMask(ones, bits int) IPMask

CIDRMask返回一个IPMask类型值，该返回值总共有bits个字位，其中前ones个字位都是1，其他字位都是0。

func (IPMask) Size

func (m IPMask) Size() (ones, bits int)

Size返回m的前导的1字位数和总字位数。若是m不是规范的子网掩码（字位：/^1+0+$/），将返会(0, 0)。

func (IPMask) String

func (m IPMask) String() string

String返回m的十六进制格式，没有标点。

type IPNet

type IPNet struct { IP IP // 网络地址 Mask IPMask // 子网掩码 }

IPNet表示一个IP网络。

func (*IPNet) Contains

func (n *IPNet) Contains(ip IP) bool

Contains报告该网络是否包含地址ip。

func (*IPNet) Network

func (n *IPNet) Network() string

Network返回网络类型名："ip+net"，注意该类型名是不合法的。

func (*IPNet) String

func (n *IPNet) String() string

String返回n的CIDR表示，如"192.168.100.1/24"或"2001:DB8::/48"，参见RFC 4632和RFC 4291。

若是n的Mask字段不是规范格式，它会返回一个包含n.IP.String()、斜线、n.Mask.String()（此时表示为无标点十六进制格式）的字符串，如"192.168.100.1/c000ff00"。

举例：

package main 
import(
    "fmt"
    "net"
    // "log"
    // "reflect"
)

var ipNetContainsTests = []struct {
    ip  net.IP
    net *net.IPNet
    ok  bool
}{
    {net.IPv4(172, 16, 1, 1), &net.IPNet{IP: net.IPv4(172, 16, 0, 0), Mask: net.CIDRMask(12, 32)}, true},
    {net.IPv4(172, 24, 0, 1), &net.IPNet{IP: net.IPv4(172, 16, 0, 0), Mask: net.CIDRMask(13, 32)}, false},
    {net.IPv4(192, 168, 0, 3), &net.IPNet{IP: net.IPv4(192, 168, 0, 0), Mask: net.IPv4Mask(0, 0, 255, 252)}, true},
    {net.IPv4(192, 168, 0, 4), &net.IPNet{IP: net.IPv4(192, 168, 0, 0), Mask: net.IPv4Mask(0, 255, 0, 252)}, false},
    {net.ParseIP("2001:db8:1:2::1"), &net.IPNet{IP: net.ParseIP("2001:db8:1::"), Mask: net.CIDRMask(47, 128)}, true},
    {net.ParseIP("2001:db8:1:2::1"), &net.IPNet{IP: net.ParseIP("2001:db8:2::"), Mask: net.CIDRMask(47, 128)}, false},
    {net.ParseIP("2001:db8:1:2::1"), &net.IPNet{IP: net.ParseIP("2001:db8:1::"), Mask: net.IPMask(net.ParseIP("ffff:0:ffff::"))}, true},
    {net.ParseIP("2001:db8:1:2::1"), &net.IPNet{IP: net.ParseIP("2001:db8:1::"), Mask: net.IPMask(net.ParseIP("0:0:0:ffff::"))}, false},
}

func main() {
    for _, tt := range ipNetContainsTests {
        if ok := tt.net.Contains(tt.ip); ok != tt.ok {
            fmt.Errorf("IPNet(%v).Contains(%v) = %v, want %v", tt.net, tt.ip, ok, tt.ok)
        }else{
            fmt.Printf("string is : %s\n", tt.net.String())
            fmt.Printf("network is : %s\n",tt.net.Network())
        }
    }
}

userdeMBP:go-learning user$ go run test.go
string is : 172.16.0.0/12
network is : ip+net
string is : 172.16.0.0/13
network is : ip+net
string is : 192.168.0.0/0000fffc
network is : ip+net
string is : 192.168.0.0/00ff00fc
network is : ip+net
string is : 2001:db8:1::/47
network is : ip+net
string is : 2001:db8:2::/47
network is : ip+net
string is : 2001:db8:1::/ffff0000ffff00000000000000000000
network is : ip+net
string is : 2001:db8:1::/000000000000ffff0000000000000000
network is : ip+net

2）实现TCP Socket——TCPConn、TCPAddr、TCPListener

客户端使用的三个方法

type TCPConn

type TCPConn struct {
    // 内含隐藏或非导出字段
}

TCPConn表明一个TCP网络链接，实现了Conn接口。

func DialTCP

func DialTCP(net string, laddr, raddr *TCPAddr) (*TCPConn, error)

DialTCP在网络协议net上链接本地地址laddr和远端地址raddr。

参数net必须是"tcp"、"tcp4"、"tcp6"，表示(IPv4\IPv6任意一个)、(IPv4-only)或者(IPv6-only)；

laddr表示本机地址，通常为nil.若是laddr不是nil，将使用它做为本地地址，即客户端，不然自动选择一个本地地址；

raddr表示远程的服务地址，即服务端

func (*TCPConn) Read

func (c *TCPConn) Read(b []byte) (int, error)

Read实现了Conn接口Read方法，客户端读取服务端响应回来的内容

func (*TCPConn) Write

func (c *TCPConn) Write(b []byte) (int, error)

Write实现了Conn接口Write方法，客户端将请求写入conn中发送给服务端

控制TCP链接函数有：

func (*TCPConn) SetKeepAlive

func (c *TCPConn) SetKeepAlive(keepalive bool) error

SetKeepAlive设置操做系统是否应该在该链接中发送keepalive信息

type TCPAddr

type TCPAddr struct {
    IP   IP
    Port int
    Zone string // IPv6范围寻址域
}

TCPAddr表明一个TCP终端地址。

func ResolveTCPAddr

func ResolveTCPAddr(net, addr string) (*TCPAddr, error)

ResolveTCPAddr将addr做为TCP地址解析并返回。

参数addr表示域名或IP地址，如“www.baidu.com:80”或“127.0.0.1:22”。格式为"host:port"或"[ipv6-host%zone]:port"，解析获得网络名和端口名；

net参数必须是"tcp"、"tcp4"或"tcp6"，表示(IPv4\IPv6任意一个)、(IPv4-only)或者(IPv6-only)。

IPv6地址字面值/名称必须用方括号包起来，如"[::1]:80"、"[ipv6-host]:http"或"[ipv6-host%zone]:80"。

服务端实现监听使用的函数：

type TCPListener

type TCPListener struct {
    // 内含隐藏或非导出字段
}

TCPListener表明一个TCP网络的监听者。使用者应尽可能使用Listener接口而不是假设（网络链接为）TCP。

func ListenTCP

func ListenTCP(net string, laddr *TCPAddr) (*TCPListener, error)

ListenTCP在本地TCP地址laddr上声明并返回一个*TCPListener，net参数必须是"tcp"、"tcp4"、"tcp6"，若是laddr的端口字段为0，函数将选择一个当前可用的端口，能够用Listener的Addr方法得到该端口。

func (*TCPListener) Accept

func (l *TCPListener) Accept() (Conn, error)

Accept用于实现Listener接口的Accept方法；他会等待下一个呼叫，并返回一个该呼叫的Conn接口。

适用上面的函数实现的客户端和服务端实现简单的时间同步服务，监听1200端口

客户端为：

package main 
import(
    "fmt"
    "net"
    "os"
)

func checkError(index int, err error){
    if err != nil{
        fmt.Fprintf(os.Stderr, "index : %v,Fatal error : %s", index, err.Error())
        os.Exit(1)
    }
}

func main() {
    if len(os.Args) != 2 {
        fmt.Fprintf(os.Stderr, "Usage: %s host:port", os.Args[0])
        os.Exit(1)
    }
    service := os.Args[1]
    tcpAddr, err := net.ResolveTCPAddr("tcp4", service)
    checkError(1, err)

    //建立一个TCP链接conn
    conn, err := net.DialTCP("tcp", nil, tcpAddr)
    checkError(2, err)

    //经过conn来发送请求信息
    _, err = conn.Write([]byte("HEAD / HTTP/1.0 \r\n\r\n"))
    checkError(3, err)


    //从conn中读取服务端返回的所有的文本
    rsp := make([]byte, 64)
    n, err := conn.Read(rsp)
    checkError(4, err)
    fmt.Printf("receive %d bytes in response : %q\n", n, rsp[:n])

    os.Exit(0)
}

服务端为：

package main 
import(
    "fmt"
    "net"
    "os"
    "time"
)

func checkError(err error){
    if err != nil{
        fmt.Fprintf(os.Stderr, "Fatal error : %s", err.Error())
        os.Exit(1)
    }
}

func main() {
    service := ":1200"
    tcpAddr, err := net.ResolveTCPAddr("tcp4", service)
    checkError(err)

    listener, err := net.ListenTCP("tcp", tcpAddr)
    checkError(err)

    for{ 
        conn, err := listener.Accept()
        if err != nil{
            continue
        }
        go handleerClient(conn)
    }
}

func handleerClient(conn net.Conn){
    defer conn.Close() 
    daytime := time.Now().String()
    conn.Write([]byte(daytime))
}

客户端返回：

userdeMBP:go-learning user$ go run test.go 127.0.0.1:1200
receive 51 bytes in response : "2019-02-27 15:25:02.113373 +0800 CST m=+5.168778770"

3）实现UDP Socket — UDPConn、UDPAddr

type UDPConn

type UDPConn struct {
    // 内含隐藏或非导出字段
}

UDPConn表明一个UDP网络链接，实现了Conn和PacketConn接口。

func DialUDP

func DialUDP(net string, laddr, raddr *UDPAddr) (*UDPConn, error)

DialTCP在网络协议net上链接本地地址laddr和远端地址raddr。net必须是"udp"、"udp4"、"udp6"；若是laddr不是nil，将使用它做为本地地址，不然自动选择一个本地地址。

func ListenUDP

func ListenUDP(net string, laddr *UDPAddr) (*UDPConn, error)

ListenUDP建立一个接收目的地是本地地址laddr的UDP数据包的网络链接。net必须是"udp"、"udp4"、"udp6"；若是laddr端口为0，函数将选择一个当前可用的端口，能够用Listener的Addr方法得到该端口。返回的*UDPConn的ReadFrom和WriteTo方法能够用来发送和接收UDP数据包（每一个包均可得到来源地址或设置目标地址）。

func (*UDPConn) Read

func (c *UDPConn) Read(b []byte) (int, error)

Read实现Conn接口Read方法

func (*UDPConn) ReadFrom

func (c *UDPConn) ReadFrom(b []byte) (int, Addr, error)

ReadFrom实现PacketConn接口ReadFrom方法

func (*UDPConn) ReadFromUDP

func (c *UDPConn) ReadFromUDP(b []byte) (n int, addr *UDPAddr, err error)

ReadFromUDP从c读取一个UDP数据包，将有效负载拷贝到b，返回拷贝字节数和数据包来源地址。

ReadFromUDP方法会在超过一个固定的时间点以后超时，并返回一个错误。

func (*UDPConn) Write

func (c *UDPConn) Write(b []byte) (int, error)

Write实现Conn接口Write方法

func (*UDPConn) WriteTo

func (c *UDPConn) WriteTo(b []byte, addr Addr) (int, error)

WriteTo实现PacketConn接口WriteTo方法

func (*UDPConn) WriteToUDP

func (c *UDPConn) WriteToUDP(b []byte, addr *UDPAddr) (int, error)

WriteToUDP经过c向地址addr发送一个数据包，b为包的有效负载，返回写入的字节。

WriteToUDP方法会在超过一个固定的时间点以后超时，并返回一个错误。在面向数据包的链接上，写入超时是十分罕见的。

type UDPAddr

type UDPAddr struct {
    IP   IP
    Port int
    Zone string // IPv6范围寻址域
}

UDPAddr表明一个UDP终端地址。

func ResolveUDPAddr

func ResolveUDPAddr(net, addr string) (*UDPAddr, error)

ResolveTCPAddr将addr做为TCP地址解析并返回。参数addr格式为"host:port"或"[ipv6-host%zone]:port"，解析获得网络名和端口名；net必须是"udp"、"udp4"或"udp6"。

IPv6地址字面值/名称必须用方括号包起来，如"[::1]:80"、"[ipv6-host]:http"或"[ipv6-host%zone]:80"。

客户端：

package main 
import(
    "fmt"
    "net"
    "os"
)

func checkError(index int, err error){
    if err != nil{
        fmt.Fprintf(os.Stderr, "index : %v,Fatal error : %s", index, err.Error())
        os.Exit(1)
    }
}

func main() {
    if len(os.Args) != 2 {
        fmt.Fprintf(os.Stderr, "Usage: %s host:port", os.Args[0])
        os.Exit(1)
    }
    service := os.Args[1]
    udpAddr, err := net.ResolveUDPAddr("udp", service)
    checkError(1, err)

    //建立一个TCP链接conn
    conn, err := net.DialUDP("udp", nil, udpAddr)
    defer conn.Close()
    checkError(2, err)

    //经过conn来发送请求信息
    _, err = conn.Write([]byte("anything"))
    checkError(3, err)

    //从conn中读取服务端返回的所有的文本
    var rsp [512]byte
    n, err := conn.Read(rsp[0:])
    checkError(4, err)

    fmt.Printf("receive %d bytes in response : %q\n", n, rsp[:n])
    os.Exit(0)
}

服务端

package main 
import(
    "fmt"
    "net"
    "os"
    "time"
)

func checkError(err error){
    if err != nil{
        fmt.Fprintf(os.Stderr, "Fatal error : %s", err.Error())
        os.Exit(1)
    }
}

func main() {
    service := ":11200"
    udpAddr, err := net.ResolveUDPAddr("udp", service)
    checkError(err)

    conn, err := net.ListenUDP("udp", udpAddr)
    defer conn.Close()
    checkError(err)

    for{ 
        go handlerClient(conn)
    }
}

func handlerClient(conn *net.UDPConn){
    var rsp [512]byte
    _, addr, err := conn.ReadFromUDP(rsp[0:])
    if err != nil{
        return
    }
    daytime := time.Now().String()
    conn.WriteToUDP([]byte(daytime), addr)
}

客户端返回：

userdeMBP:go-learning user$ go run test.go 127.0.0.1:11200
receive 51 bytes in response : "2019-02-27 16:25:46.905443 +0800 CST m=+2.197257345"

）查询操做

func LookupHost

func LookupHost(host string) (addrs []string, err error)

LookupHost函数查询主机的网络地址序列。

func LookupIP

func LookupIP(host string) (addrs []IP, err error)

LookupIP函数查询主机的ipv4和ipv6地址序列。

举例：

package main 
import(
    "fmt"
    "net"
    "reflect"
)

var parseIPTests = []struct {
    in  string
    out net.IP
}{
    {"127.0.1.2", net.IPv4(127, 0, 1, 2)},
    {"127.0.0.1", net.IPv4(127, 0, 0, 1)},
    {"127.001.002.003", net.IPv4(127, 1, 2, 3)},
    {"::ffff:127.1.2.3", net.IPv4(127, 1, 2, 3)},
    {"::ffff:127.001.002.003", net.IPv4(127, 1, 2, 3)},
    {"::ffff:7f01:0203", net.IPv4(127, 1, 2, 3)},
    {"0:0:0:0:0000:ffff:127.1.2.3", net.IPv4(127, 1, 2, 3)},
    {"0:0:0:0:000000:ffff:127.1.2.3", net.IPv4(127, 1, 2, 3)},
    {"0:0:0:0::ffff:127.1.2.3", net.IPv4(127, 1, 2, 3)},

    {"2001:4860:0:2001::68", net.IP{0x20, 0x01, 0x48, 0x60, 0, 0, 0x20, 0x01, 0, 0, 0, 0, 0, 0, 0x00, 0x68}},
    {"2001:4860:0000:2001:0000:0000:0000:0068", net.IP{0x20, 0x01, 0x48, 0x60, 0, 0, 0x20, 0x01, 0, 0, 0, 0, 0, 0, 0x00, 0x68}},
}

func main() {
    _, err := net.LookupIP("")
    if err == nil {
        fmt.Errorf(`LookupIP("") succeeded, should fail`)
    }
    _, err = net.LookupHost("")
    if err == nil {
        fmt.Errorf(`LookupIP("") succeeded, should fail`)
    }

    // Test that LookupHost and LookupIP, which normally
    // expect host names, work with IP addresses.
    for i, tt := range parseIPTests {
        if tt.out != nil { 
            addrs, err := net.LookupHost(tt.in)
            //len(addrs)应该等于1，addrs[0]应该为tt.in，err应该为nil，不然报错
            if len(addrs) != 1 || addrs[0] != tt.in || err != nil {
                fmt.Errorf("LookupHost(%q) = %v, %v, want %v, nil", tt.in, addrs, err, []string{tt.in})
            }else{
                fmt.Printf("%v LookupHost() addrs is : %v\n", i, addrs )
            }
        }

        if tt.out != nil {
            ips, err := net.LookupIP(tt.in)
            //len(ips)应该为1，ips[0]应该为等于tt.out，err应该为nil
            if len(ips) != 1 || !reflect.DeepEqual(ips[0], tt.out) || err != nil {
                fmt.Errorf("LookupIP(%q) = %v, %v, want %v, nil", tt.in, ips, err, []net.IP{tt.out})
            }else{
                fmt.Printf("%v LookupIP() ips is : %v\n", i, ips )
            }
        }
    }
}

userdeMBP:go-learning user$ go run test.go 127.0.0.1
0 LookupHost() addrs is : [127.0.1.2]
0 LookupIP() ips is : [127.0.1.2]
1 LookupHost() addrs is : [127.0.0.1]
1 LookupIP() ips is : [127.0.0.1]
2 LookupHost() addrs is : [127.001.002.003]
2 LookupIP() ips is : [127.1.2.3]
3 LookupHost() addrs is : [::ffff:127.1.2.3]
3 LookupIP() ips is : [127.1.2.3]
4 LookupHost() addrs is : [::ffff:127.001.002.003]
4 LookupIP() ips is : [127.1.2.3]
5 LookupHost() addrs is : [::ffff:7f01:0203]
5 LookupIP() ips is : [127.1.2.3]
6 LookupHost() addrs is : [0:0:0:0:0000:ffff:127.1.2.3]
6 LookupIP() ips is : [127.1.2.3]
7 LookupHost() addrs is : [0:0:0:0:000000:ffff:127.1.2.3]
7 LookupIP() ips is : [127.1.2.3]
8 LookupHost() addrs is : [0:0:0:0::ffff:127.1.2.3]
8 LookupIP() ips is : [127.1.2.3]
9 LookupHost() addrs is : [2001:4860:0:2001::68]
9 LookupIP() ips is : [2001:4860:0:2001::68]
10 LookupHost() addrs is : [2001:4860:0000:2001:0000:0000:0000:0068]
10 LookupIP() ips is : [2001:4860:0:2001::68]

func LookupAddr

func LookupAddr(addr string) (name []string, err error)

LookupAddr查询某个地址，返回映射到该地址的主机名序列，本函数和LookupHost不互为反函数。

未完待续