针对Linux系统：有1、2、3、4四种方法
针对Windows系统：有2、5两种通用方法
一般情况下使用"telnet ip port"判断端口通不通，其实测试方法不止这一种，还有很多种方法，下面小编给大家分享了几种方法，具体内容请往下看：
准备环境
启动一个web服务器，提供端口.
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[wyq@localhost ~]$ python -m SimpleHTTPServer 8080
Serving HTTP on 0.0.0.0 port 8080 …
用其它web服务器提供端口也一样，由于python比较方便，这里就用它
1、使用telnet判断
telnet是windows标准服务，可以直接用；如果是linux机器，需要安装telnet.
用法: telnet ip port
1）先用telnet连接不存在的端口
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[root@localhost ~] # telnet 10.0.250.3 80
Trying 10.0.250.3…
telnet: connect to address 10.0.250.3: Connection refused #直接提示连接被拒绝
2）再连接存在的端口
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[root@localhost ~] # telnet localhost 22
Trying ::1…
Connected to localhost. #看到Connected就连接成功了
Escape character is '^]' .
SSH-2.0-OpenSSH_5.3
a
Protocol mismatch.
Connection closed by foreign host.
2、使用ssh判断
ssh是linux的标准配置并且最常用，可以用来判断端口吗？
用法: ssh -v -p port username@ip
-v 调试模式(会打印日志).
-p 指定端口
username可以随意
1）连接不存在端口
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[root@localhost ~] # ssh 10.0.250.3 -p 80
ssh : connect to host 10.0.250.3 port 80: Connection refused
[root@localhost ~] # ssh 10.0.250.3 -p 80 -v
OpenSSH_5.3p1, OpenSSL 1.0.1e-fips 11 Feb 2013
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug1: Connecting to 10.0.250.3 [10.0.250.3] port 80.
debug1: connect to address 10.0.250.3 port 80: Connection refused
ssh : connect to host 10.0.250.3 port 80: Connection refused
2）连接存在的端口
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[root@localhost ~] # ssh … -p
a
^]
^C
[root@localhost ~] # ssh … -p -v
OpenSSH_.p, OpenSSL ..e-fips Feb
debug: Reading configuration data /etc/ssh/ssh_config
debug: Applying options for *
debug: Connecting to … […] port .
debug: Connection established.
debug: permanently_set_uid: /
debug: identity file /root/ . ssh /identity type –
debug: identity file /root/ . ssh /identity-cert type –
debug: identity file /root/ . ssh /id_rsa type –
debug: identity file /root/ . ssh /id_rsa-cert type –
debug: identity file /root/ . ssh /id_dsa type –
debug: identity file /root/ . ssh /id_dsa-cert type –
a
^C
不用-v选项也可以咯
3、使用wget判断
wget是linux下的下载工具，需要先安装.
用法: wget ip:port
1）连接不存在的端口
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[root@localhost ~] # wget …:
—- ::– http: // …/
Connecting to …:… failed: Connection refused.
2）连接存在的端口
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[root@localhost ~] # wget …:
—- ::– http: // …:/
Connecting to …:… connected.
HTTP request sent, awaiting response…
4、使用端口扫描工具
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[root@localhost ~] # nmap … -p
Starting Nmap . ( http: //nmap .org ) at — : CST
Nmap scan report for …
Host is up (.s latency).
PORT STATE SERVICE
/tcp closed http
MAC Address: B:A::CF:FD:D (Unknown)
Nmap done : IP address ( host up) scanned in . seconds
[root@localhost ~] # nmap … -p
Starting Nmap . ( http: //nmap .org ) at — : CST
Nmap scan report for …
Host is up (.s latency).
PORT STATE SERVICE
/tcp open http-proxy
MAC Address: B:A::CF:FD:D (Unknown)
Nmap done : IP address ( host up) scanned in . seconds
[root@localhost ~] # nmap …
Starting Nmap . ( http: //nmap .org ) at — : CST
Nmap scan report for …
Host is up (.s latency).
Not shown: closed ports
PORT STATE SERVICE
/tcp open ssh
/tcp open rpcbind
/tcp open http-proxy
/tcp open unknown
MAC Address: B:A::CF:FD:D (Unknown)
Nmap done : IP address ( host up) scanned in . seconds
5、使用专用工具tcping进行访问：
下载软件地址：https://elifulkerson.com/projects/tcping.php，如果无法下载可以从本人资源中下载
总结
提供端口服务，则使用了tcp协议，上面是以web服务器为例。如果服务器是更简单的tcp服务器，三个工具同样适用.
三个工具的共同点是：1.以tcp协议为基础；2.能访问指定端口. 遵循这两点可以找到很多工具.
一般在windows下使用tcping比较方便，linux下个人就比较喜欢用wget.
原文链接：https://blog.csdn.net/swazer_z/article/details/64442730