OpenSsl

我们常使用telnet，来探测远程服务器中，某个端口是否是打开的。

我们现在可以使用openssl，来替代telnet

Doc

refer to : https://www.openssl.org/docs/man3.0/man1/

安装

sudo dnf install openssl
 openssl version

验证端口访问

refer to : https://www.openssl.org/docs/man3.0/man1/openssl-s_client.html
https://www.openssl.org/docs/man3.0/man1/s_client.html

[root@VM-0-14-opencloudos ~]# openssl s_client  -connect 221.181.222.135:8086
CONNECTED(00000003)
140478822508352:error:1408F10B:SSL routines:ssl3_get_record:wrong version number:ssl/record/ssl3_record.c:332:
---
no peer certificate available
---
No client certificate CA names sent
---
SSL handshake has read 5 bytes and written 289 bytes
Verification: OK
---
New, (NONE), Cipher is (NONE)
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
Early data was not sent
Verify return code: 0 (ok)
---

可以看到，221.181.222.135的8086端口，是打开的。

下面，我们看一个端口关闭的例子:

[root@VM-0-14-opencloudos ~]# openssl s_client  -connect 221.181.222.135:15666
140389772629824:error:0200206F:system library:connect:Connection refused:crypto/bio/b_sock2.c:110:
140389772629824:error:2008A067:BIO routines:BIO_connect:connect error:crypto/bio/b_sock2.c:111:
connect:errno=111

Nmap

refer to: https://nmap.org/book/inst-windows.html

https://zhuanlan.zhihu.com/p/585377081

探测端口

nmap -p 8082 221.181.222.135

同时探测多个端口：

nmap 192.168.31.180 -p 1-80
nmap 192.168.31.180 -p 80,3389,22,21
nmap 192.168.31.180 -p 1-65535

Netcat

netcat是网络工具中的瑞士军刀，它能通过TCP和UDP在网络中读写数据。

安装：

yum install netcat 

# 查看是否安装成功
nc –help

端口扫描的语法

nc [-options] [HostName or IP] [PortNumber]

示例如下：

[root@outgateway ~]# nc -zvw3 192.168.33.15 1883
Ncat: Version 7.92 ( https://nmap.org/ncat )
Ncat: Connected to 192.168.33.15:1883.
Ncat: 0 bytes sent, 0 bytes received in 0.01 seconds.


[root@outgateway ~]# 
[root@outgateway ~]# 


[root@outgateway ~]# nc -zvw3 192.168.33.15 1882
Ncat: Version 7.92 ( https://nmap.org/ncat )
Ncat: No route to host.

命令详解：

nc：即执行的命令主体；
z：零 I/O 模式（被用来扫描）；
v：显式地输出；
w3：设置超时时间为 3 秒；