TCP 端口扫描器

非并发版本

package main

import (
	"fmt"
	"net"
)

func main() {
	for i := 21; i < 120; i++ {
		address := fmt.Sprintf("192.168.1.1:%d", j)
		conn, err := net.Dial("tcp", address)
		if err != nil {
			fmt.Printf("%s关闭了\n", address)
			continue
		}
		conn.Close()
		fmt.Printf("%s 打开了!!!\n", address)
	}
}

并发版本

package main

import (
	"fmt"
	"net"
	"sync"
	"time"
)

func main() {
	start := time.Now()
	var wg sync.WaitGroup
	for i := 21; i < 120; i++ {
		wg.Add(1)
		go func(j int) {
			defer wg.Done()
			address := fmt.Sprintf("192.168.1.1:%d", j)
			conn, err := net.Dial("tcp", address)
			if err != nil {
				//fmt.Printf("%s关闭了\n", address)
				return
			}
			conn.Close()
			fmt.Printf("%s 打开了!!!\n", address)
		}(i)

	}
	wg.Wait()
	elapsed := time.Since(start) / 1e9
	fmt.Printf("/n/n%d seconds", elapsed)
}

goroutine 池并发版 TCP 端口扫描器

创建固定数量的m个goroutine（代码中创建了500个），利用channel的机制，往channel中传递n个数据，然后分配给这m个goroutine，m<=n。对带缓存的channel不理解的可以看一下通道缓冲区 。

package main

import (
	"fmt"
	"net"
	"sort"
	"time"
)

func worker(ports chan int, results chan int) {
	for p := range ports {
		address := fmt.Sprintf("192.168.10.11:%d", p)
		conn, err := net.Dial("tcp", address)
		//失败
		if err != nil {
			results <- 0
			continue
		}
		conn.Close()
		//成功
		results <- p
	}
}

func main() {
	start := time.Now()

	ports := make(chan int, 100)
	results := make(chan int)

	//采用slice类型保存结果
	var openports []int
	var closeports []int

	//创建500个goroutine
	for i := 0; i < 500; i++ {
		go worker(ports, results)
	}

	//发送任务 需要单独的goroutine
	go func() {
		for i := 1; i < 65535; i++ {
			ports <- i
		}
	}()

	//接收结果 在主goroutine中完成
	for i := 1; i < 65535; i++ {
		port := <-results
		if port != 0 {
			openports = append(openports, port)
		} else {
			closeports = append(closeports, port)
		}
	}

	close(ports)
	close(results)

	sort.Ints(openports)
	sort.Ints(closeports)

	for _, port := range openports {
		fmt.Printf("%d open\n", port)
	}

	//for _, port := range closeports {
	//	fmt.Printf("%d closed\n", port)
	//}

	elapsed := time.Since(start) / 1e9
	fmt.Printf("\n\n%d seconds", elapsed)
}

运行

$ go build && m
25 open
.
.
.
902 open
912 open

22 seconds

测试中发现，把500个goroutine改为20000个，速度是变快了，但结果并不准确。

time.Since

func Since

func Since(t Time) Duration

Since returns the time elapsed since t. It is shorthand for time.Now().Sub(t).

Since返回自t以来经过的时间。它是时间的简写。Now().Sub(t).

net包Conn 接口

type Conn interface {
	// Read reads data from the connection.
	// Read can be made to time out and return an error after a fixed
	// time limit; see SetDeadline and SetReadDeadline.
	Read(b []byte) (n int, err error)

	// Write writes data to the connection.
	// Write can be made to time out and return an error after a fixed
	// time limit; see SetDeadline and SetWriteDeadline.
	Write(b []byte) (n int, err error)

	// Close closes the connection.
	// Any blocked Read or Write operations will be unblocked and return errors.
	Close() error

	// LocalAddr returns the local network address, if known.
	LocalAddr() Addr

	// RemoteAddr returns the remote network address, if known.
	RemoteAddr() Addr

	// SetDeadline sets the read and write deadlines associated
	// with the connection. It is equivalent to calling both
	// SetReadDeadline and SetWriteDeadline.
	//
	// A deadline is an absolute time after which I/O operations
	// fail instead of blocking. The deadline applies to all future
	// and pending I/O, not just the immediately following call to
	// Read or Write. After a deadline has been exceeded, the
	// connection can be refreshed by setting a deadline in the future.
	//
	// If the deadline is exceeded a call to Read or Write or to other
	// I/O methods will return an error that wraps os.ErrDeadlineExceeded.
	// This can be tested using errors.Is(err, os.ErrDeadlineExceeded).
	// The error's Timeout method will return true, but note that there
	// are other possible errors for which the Timeout method will
	// return true even if the deadline has not been exceeded.
	//
	// An idle timeout can be implemented by repeatedly extending
	// the deadline after successful Read or Write calls.
	//
	// A zero value for t means I/O operations will not time out.
	SetDeadline(t time.Time) error

	// SetReadDeadline sets the deadline for future Read calls
	// and any currently-blocked Read call.
	// A zero value for t means Read will not time out.
	SetReadDeadline(t time.Time) error

	// SetWriteDeadline sets the deadline for future Write calls
	// and any currently-blocked Write call.
	// Even if write times out, it may return n > 0, indicating that
	// some of the data was successfully written.
	// A zero value for t means Write will not time out.
	SetWriteDeadline(t time.Time) error
}

Conn is a generic stream-oriented network connection.
Conn是一种通用的面向流的网络连接。

Multiple goroutines may invoke methods on a Conn simultaneously.
多个goroutine可以同时调用一个Conn上的方法。

func Dial

func Dial(network, address string) (Conn, error)

Dial connects to the address on the named network.
拨号连接到命名网络上的地址。

Known networks are “tcp”, “tcp4” (IPv4-only), “tcp6” (IPv6-only), “udp”, “udp4” (IPv4-only), “udp6” (IPv6-only), “ip”, “ip4” (IPv4-only), “ip6” (IPv6-only), “unix”, “unixgram” and “unixpacket”.

For TCP and UDP networks, the address has the form “host:port”. The host must be a literal IP address, or a host name that can be resolved to IP addresses. The port must be a literal port number or a service name. If the host is a literal IPv6 address it must be enclosed in square brackets, as in “[2001:db8::1]:80” or “[fe80::1%zone]:80”. The zone specifies the scope of the literal IPv6 address as defined in RFC 4007. The functions JoinHostPort and SplitHostPort manipulate a pair of host and port in this form. When using TCP, and the host resolves to multiple IP addresses, Dial will try each IP address in order until one succeeds.

Examples:

Dial("tcp", "golang.org:http")
Dial("tcp", "192.0.2.1:http")
Dial("tcp", "198.51.100.1:80")
Dial("udp", "[2001:db8::1]:domain")
Dial("udp", "[fe80::1%lo0]:53")
Dial("tcp", ":80")

For IP networks, the network must be “ip”, “ip4” or “ip6” followed by a colon and a literal protocol number or a protocol name, and the address has the form “host”. The host must be a literal IP address or a literal IPv6 address with zone. It depends on each operating system how the operating system behaves with a non-well known protocol number such as “0” or “255”.

Examples:

Dial("ip4:1", "192.0.2.1")
Dial("ip6:ipv6-icmp", "2001:db8::1")
Dial("ip6:58", "fe80::1%lo0")

For TCP, UDP and IP networks, if the host is empty or a literal unspecified IP address, as in “:80”, “0.0.0.0:80” or “[::]:80” for TCP and UDP, “”, “0.0.0.0” or “::” for IP, the local system is assumed.

For Unix networks, the address must be a file system path.

func DialTimeout

func DialTimeout(network, address string, timeout time.Duration) (Conn, error)

DialTimeout acts like Dial but takes a timeout.
DialTimeout的作用类似于Dial，但需要超时。

The timeout includes name resolution, if required. When using TCP, and the host in the address parameter resolves to multiple IP addresses, the timeout is spread over each consecutive dial, such that each is given an appropriate fraction of the time to connect.

See func Dial for a description of the network and address parameters.

func FileConn

func FileConn(f *os.File) (c Conn, err error)

FileConn returns a copy of the network connection corresponding to the open file f. It is the caller’s responsibility to close f when finished. Closing c does not affect f, and closing f does not affect c.
FileConn返回与打开的文件f相对应的网络连接的副本。完成后关闭f是调用者的责任。关闭c不影响f，关闭f不影响c。