网络端口检测实战

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背景

一般在进行网络访问不通的时候需要进行端口测试，在windows环境下，可以使用telnet命令进行检测：

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telnet www.baidu.com 443

telnet检测仅适用于tcp协议的端口检测，对于udp协议的则毫无办法。

在Liunx和macOS环境下，默认是没有安装的telnet的，但是有nc这工具。试用了一下发现检测效果更佳。

NC网络检测实战

  • tcp检测

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    zhengkaideMacBook-Pro:~ zhengk$ nc -z -v 220.181.38.148 80
    found 0 associations
    found 1 connections:
         1:	flags=82<CONNECTED,PREFERRED>
    	outif en0
    	src 192.168.31.68 port 64654
    	dst 220.181.38.148 port 80
    	rank info not available
    	TCP aux info available

    Connection to 220.181.38.148 port 80 [tcp/http] succeeded!

  • udp检测

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    zhengkaideMacBook-Pro:~ zhengk$ nc -u -z -v 220.181.38.148 80
    found 0 associations
    found 1 connections:
         1:	flags=82<CONNECTED,PREFERRED>
    	outif (null)
    	src 192.168.31.68 port 60536
    	dst 220.181.38.148 port 80
    	rank info not available

    Connection to 220.181.38.148 port 80 [udp/http] succeeded!

  • 范围端口检测

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    zhengkaideMacBook-Pro:~ zhengk$ nc -z -v -G 2 220.181.38.148 75-80
      nc: connectx to 220.181.38.148 port 75 (tcp) failed: Operation timed out
      nc: connectx to 220.181.38.148 port 76 (tcp) failed: Operation timed out
      nc: connectx to 220.181.38.148 port 77 (tcp) failed: Operation timed out
      nc: connectx to 220.181.38.148 port 78 (tcp) failed: Operation timed out
      nc: connectx to 220.181.38.148 port 79 (tcp) failed: Operation timed out
      found 0 associations
      found 1 connections:
           1:	flags=82<CONNECTED,PREFERRED>
      	outif en0
      	src 192.168.31.68 port 64689
      	dst 220.181.38.148 port 80
      	rank info not available
      	TCP aux info available
      
      Connection to 220.181.38.148 port 80 [tcp/http] succeeded!

扩展

在macOS的环境下，nc命令的使用参数与linux环境下的参数代表的并不一样，这需要特别注意，常用的几个参数如下：

  • -G：用来指定判断超时的时间，比如-G 2就指2秒就算超时。注意：在linux中，使用-w参数来指定超时
  • -v:用于输出交互过程。
  • -z:在端口扫描的情况下使用，否则不会自动退出结束。

更多的参数配置可以使用-h来获取帮助：

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zhengkaideMacBook-Pro:~ zhengk$ nc -h
usage: nc [-46AacCDdEFhklMnOortUuvz] [-K tc] [-b boundif] [-i interval] [-p source_port] [--apple-delegate-pid pid] [--apple-delegate-uuid uuid]
	  [-s source_ip_address] [-w timeout] [-X proxy_version]
	  [-x proxy_address[:port]] [hostname] [port[s]]
	Command Summary:
		-4		Use IPv4
		-6		Use IPv6
		-A		Set SO_RECV_ANYIF on socket
		-a		Set SO_AWDL_UNRESTRICTED on socket
		-b ifbound	Bind socket to interface
		-c		Send CRLF as line-ending
		-C		Don't use cellular connection
		-D		Enable the debug socket option
		-d		Detach from stdin
		-E		Don't use expensive interfaces
		-F		Do not use flow advisory (flow adv enabled by default)
		-G conntimo	Connection timeout in seconds
		-h		This help text
		-H keepidle	Initial idle timeout in seconds
		-I keepintvl	Interval for repeating idle timeouts in seconds
		-i secs		Delay interval for lines sent, ports scanned
		-J keepcnt	Number of times to repeat idle timeout
		-k		Keep inbound sockets open for multiple connects
		-K tclass	Specify traffic class
		-l		Listen mode, for inbound connects
		-L num_probes Number of probes to send before generating a read timeout event
		-m		Set SO_INTCOPROC_ALLOW on socket
		-n		Suppress name/port resolutions
		-M		Use MULTIPATH domain socket
		-N num_probes Number of probes to send before generating a write timeout event
		-O		Use old-style connect instead of connectx
		-p port		Specify local port for remote connects (cannot use with -l)
		-r		Randomize remote ports
		-s addr		Local source address
		-t		Answer TELNET negotiation
		-U		Use UNIX domain socket
		-u		UDP mode
		-v		Verbose
		-w secs		Timeout for connects and final net reads
		-X proto	Proxy protocol: "4", "5" (SOCKS) or "connect"
		-x addr[:port]	Specify proxy address and port
		-z		Zero-I/O mode [used for scanning]
		-o		Issue socket options after connect/bind
		--apple-delegate-pid pid	Set socket as delegate using pid
	Port numbers can be individual or ranges: lo-hi [inclusive]