linux nc command

linux nc 命令

Netcat 是一款简单的Unix工具，使用UDP和TCP协议。 它是一个可靠的容易被其他程序所启用的后台操作工具。 使用它你可以轻易的建立任何连接。内建有很多实用的工具。

netcat 安装

# ubuntu 18.04
sudo apt install netcat
# centos  7
sudo yum install nc

应用案例

• 端口扫描

nc -z -v  10.10.0.103 3389  #查看主机3389端口是否启用

回显示例：

# 3389端口
Connection to 10.10.0.103 3389 port [tcp/*] succeeded!
# 80端口
Connection to 10.10.0.103 80 port [tcp/http] succeeded!
# 22端口
Connection to 10.10.0.100 22 port [tcp/ssh] succeeded!

无回显，则端口无法通信。默认TCP，-u参数可调整为UDP模式。

端口扫描案例：

For example:

           $ nc -zv host.example.com 20-30
           Connection to host.example.com 22 port [tcp/ssh] succeeded!
           Connection to host.example.com 25 port [tcp/smtp] succeeded!

     The port range was specified to limit the search to ports 20 - 30, and is
     scanned by increasing order.

     You can also specify a list of ports to scan, for example:

           $ nc -zv host.example.com 80 20 22
           nc: connect to host.example.com 80 (tcp) failed: Connection refused
           nc: connect to host.example.com 20 (tcp) failed: Connection refused
           Connection to host.example.com port [tcp/ssh] succeeded!

     The ports are scanned by the order you given.