Shulou(Shulou.com)06/01 Report--

In this issue, the editor will bring you about how to use the nc command in the Linux system. The article is rich in content and analyzes and narrates it from a professional point of view. I hope you can get something after reading this article.

Nc can provide the following network functions:

1) listen on a specific port, then nc can be used as a server, but I found that the server generated using nc is only an echo server, there is no other more powerful features.

2) connect to a specific port, and nc becomes a client. Similarly, it is also a simple client that can only play the role of echo.

3) scan the port, which can be used to query whether a port is open on a machine.

Several specific examples of use

Example 1:

Use nc to open a specific port under linux

Nc-lp 23 & (i.e. telnet)

Netstat-an | grep 23 (check whether the port is open properly)

Example 2:

Use nc for file transfer, command

Ssh root@www.freetstar.com "(nc-l 10003 > destination 2 > / dev/null &)" & & cat source | nc www.freetstar.com 10003

& & the front ssh logs in to the remote host www.freetstar.com and uses the nc command to open the local port 10003 to become a background process

After that, open the source file on the local machine and redirect it to port 10003 of www.freetstar.com, that is, let the remote www.freetstar.com host port 10003 receive source files

Example 3:

Use nc to scan specific ports under linux

Nc-v-z host.example.com 70-80

Scan ports (70 to 80), which can be specified. -v outputs details.

Example 4:

Clone a hard disk or partition

Similar to example 2, it is only necessary for dd to get the data from the hard disk or partition and transfer it.

Cloning a hard disk or partition should not be done on a system that is already mount. Therefore, you need to boot using the installation CD and boot the system after entering the rescue mode (or using the Knoppix tool CD).

Execute on server1: # nc-l-p 1234 | dd of=/dev/sda

Perform port 1234 listening on server1 and save the resulting file to / dev/sda

Execute on server2: # dd if=/dev/sda | nc server1 1234

Example 5:

Save the Web page

While true; do nc-l-p 80-Q 1

< somepage.html; done 例子6： 模拟HTTP Headers [root@hatest1 ~]# nc www.huanxiangwu.com 80 GET / HTTP/1.1 Host: ispconfig.org Referrer: mypage.com User-Agent: my-browser 在nc命令后，输入红色部分的内容，然后按两次回车，即可从对方获得HTTP Headers内容。 例子7： 聊天 server1上监听1234端口[root@hatest2 tmp]# nc -lp 1234 server2上向server1的1234端口发送消息[root@hatest1 ~]# nc server1 1234 这样，双方就可以相互交流了。使用Ctrl+D正常退出。 更多的使用，查看man手册 nc example.host port 打开与example.host主机的port的一个TCP链接.如果链接失败,不显示任何错误信息,仅仅退出 nc -p 31337 -w 5 example.host 42 打开与example。host主机的42号端口的一个TCP链接。用31337作为源端口,超时链接时间为5秒 nc -u example.host 53 指定协议为udp协议 语　　法：nc [-hlnruz][-g][-G][-i][-o][-p][-s][-v...][-w][主机名称][通信端口...] 参　　数： -g 设置路由器跃程通信网关，最多可设置8个。 -G 设置来源路由指向器，其数值为4的倍数。 -h 在线帮助。 -i 设置时间间隔，以便传送信息及扫描通信端口。 -l 使用监听模式，管控传入的资料。 -n 直接使用IP地址，而不通过域名服务器。 -o 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 设置本地主机使用的通信端口。 -r 乱数指定本地与远端主机的通信端口。 -s 设置本地主机送出数据包的IP地址。 -u 使用UDP传输协议。 -v 显示指令执行过程。 -w 设置等待连线的时间。 -z 使用0输入/输出模式，只在扫描通信端口时使用。 来看下它的基本用法: 1.监听本地端口 代码如下: 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.端口扫描 代码如下: root@10.1.1.43:~# nc -v -w 10 10.1.1.180 80 (UNKNOWN) [10.1.1.180] 80 (www) open 代码如下: 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.文件传出 源10.1.1.43 text.txt 目的 10.1.1.180 代码如下: root@10:~# nc -l -p 1234 >

Test.txt # opens port 10.1.1.180 to listen and redirects the data transmitted by socket to the test.txt file test 43 nc

Root@10.1.1.43:~#cat test.txt

Root@10.1.1.43:~# nc 10.1.1.180 1234 < test.txt # connects to the remote 10.1.1.180, and the path from test.txt is directed to socket, thus transferring the file to the distance.

Root@10:~# cat test.txt

Test 43 nc

4. Directory transfer

Source 10.1.1.43 python_program

Purpose 10.1.1.180

The code is as follows:

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

The code is as follows:

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. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0

Udp 0 0 0.0.0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 8. 0. 0. 0. 0. 0. 0. 0. 0

The code is as follows:

Root@172.16.211.35:~# nc-vuz 172.16.211.34 68

Connection to 172.16.211.34 68 port [udp/bootpc] succeeded!

This is how the nc command is used in the Linux system shared by the editor. If you happen to have similar doubts, you might as well refer to the above analysis to understand. If you want to know more about it, you are welcome to follow the industry information channel.

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