1. nc命令
语法：nc -z -v -n IPADDRESS port
-z 仅用于端口扫描，0输入输出
-v 显示指令执行过程
-n 直接使用IP地址，而不是通过域名服务器

[root@shansibleqa ~]# nc -z -v -n IP 22
Ncat: Version 7.50 ( https://nmap.org/ncat )
Ncat: Connected to IP:22.
Ncat: 0 bytes sent, 0 bytes received in 0.01 seconds.

[root@shansibleqa ~]# nc -z -v -n IP 587
Ncat: Version 7.50 ( https://nmap.org/ncat )
Ncat: Connected to IP:587.
Ncat: 0 bytes sent, 0 bytes received in 0.01 seconds.

2. wget命令
语法：wget ip:port
如果通

[root@shansibleqa ~]# wget IP:22
--2019-12-24 17:43:50--  http://IP:22/
Connecting to IP:22... connected.
HTTP request sent, awaiting response... 200 No headers, assuming HTTP/0.9
Length: unspecified

如果不通

[root@shansibleqa ~]# wget IP:80
--2019-12-24 17:43:56--  http://IP/
Connecting to IP:80... failed: No route to host.

3. shell命令
语法：ssh -v -p port IP
能够连上

[root@shansibleqa ~]# ssh -v -p 80 XX.XX.XX.XX
OpenSSH_7.4p1, OpenSSL 1.0.2k-fips  26 Jan 2017
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 58: Applying options for *
debug1: Connecting to XX.XX.XX.XX [XX.XX.XX.XX] port 80.
debug1: Connection established.
debug1: permanently_set_uid: 0/0

连不上

[root@shansibleqa ~]# ssh -v -p 23 XX.XX.XX.XX
OpenSSH_7.4p1, OpenSSL 1.0.2k-fips  26 Jan 2017
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 58: Applying options for *
debug1: Connecting to XX.XX.XX.XX [XX.XX.XX.XX] port 23.
debug1: connect to address XX.XX.XX.XX port 23: Connection timed out
ssh: connect to host XX.XX.XX.XXport 23: Connection timed out

4. curl命令
语法：curl ip:port
端口通

[root@shansibleqa ~]# curl ip:22
SSH-2.0-OpenSSH_7.4
curl: (56) Recv failure: Connection reset by peer

端口不通

[root@shansibleqa ~]# curl ip:443
curl: (52) Empty reply from server