Common usage of linux nc command

from:http://my.oschina.net/davehe/blog/261845

NetCat, known as the "Swiss Army Knife" in networking tools, has Windows and Linux versions. Because it is short, powerful and functional, it is designed as a simple and reliable network tool, which can transmit and read data through TCP or UDP protocol. At the same time, it is also a network application debug analyzer, because it can create various types of network connections as needed.

Let's take a look at its basic usage:

[email protected]:~# nc -h
[v1.10-38]
connect to somewhere:	nc [-options] hostname port[s] [ports] ... 
listen for inbound:	nc -l -p port [-options] [hostname] [port]
options:
	-c shell commands	as `-e'; use /bin/sh to exec [dangerous!!]
	-e filename		program to exec after connect [dangerous!!]
	-b			allow broadcasts
	-g gateway		source-routing hop point[s], up to 8                          设置路由器跃程通信网关，最高可设置8个。
	-G num			source-routing pointer: 4, 8, 12, ...                         设置来源路由指向器，其数值为4的倍数。
	-h			this cruft 
	-i secs			delay interval for lines sent, ports sca                      延时的间隔
        -k                      set keepalive option on socket
	-l			listen mode, for inbound connects                             监听模式,入站连接
	-n			numeric-only IP addresses, no DNS                             直接使用ip地址,而不用域名服务器
	-o file			hex dump of traffic                                           指定文件名称，把往来传输的数据以16进制字码倾倒成该文件保存。
	-p port			local port number                                             本地端口
	-r			randomize local and remote ports                              随机本地和远程端口 
	-q secs			quit after EOF on stdin and delay of secs
	-s addr			local source address  
	-T tos			set Type Of Service
	-t			answer TELNET negotiation   
	-u			UDP mode                                                      udp  模式
	-v			verbose [use twice to be more verbose]                        显示过程,vv 更多
	-w secs			timeout for connects and final net reads                      等待连接超时
	-z			zero-I/O mode [used for scanning]                             使用输入/输出模式，只在扫描通信端口时使用。

1. Listen on the local port

root@10.1.1.43:~# nc -l -p 1234 
root@10.1.1.43:~# netstat -tunlp | grep 1234
tcp        0      0 0.0.0.0:1234            0.0.0.0:*               LISTEN      15543/nc

2. Port Scan

root@10.1.1.43:~# nc -v -w 10 10.1.1.180 80
(UNKNOWN) [10.1.1.180] 80 (www) open

root@10.1.1.43:~# nc -v -w 10 10.1.1.180 -z 80-30000
(UNKNOWN) [10.1.1.180] 22000 (?) open
(UNKNOWN) [10.1.1.180] 80 (www) open

3. File outgoing

源10.1.1.43 text.txt

Purpose 10.1.1.180

root@10:~# nc -l -p 1234 > test.txt                 #开10.1.1.180:1234端口监听，并将socket传输过来的数据重定向到test.txt文件 test 43 nc
root@10.1.1.43:~#cat test.txt    

root@10.1.1.43:~# nc  10.1.1.180 1234 < test.txt    #连接远程的10.1.1.180，从test.txt的路径从定向到socket，从而将文件传输到远方。
root@10:~# cat test.txt
test 43 nc

4. Directory Transfer

source 10.1.1.43 python_program

Purpose 10.1.1.180

root@10:~# nc -l -p 1234 | tar xzvf -

root@10.1.1.43:~# tar czvf -  python_program | nc 10.1.1.180 1234
python_program/
python_program/1.py
python_program/4.py
python_program/3.py

5. Test the UDP port

root@172.16.211.34:web# netstat -tunlp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address               Foreign Address             State       PID/Program name   
tcp        0      0 0.0.0.0:22                  0.0.0.0:*                   LISTEN      1111/sshd           
udp        0      0 0.0.0.0:68                  0.0.0.0:*                               887/dhclient 


root@172.16.211.35:~# nc -vuz  172.16.211.34 68
Connection to 172.16.211.34 68 port [udp/bootpc] succeeded!

refer to:

NetCat official address: http://netcat.sourceforge.net/

Common usage of linux nc command

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