一般情況下使用"telnet ip port"判斷端口通不通，其實測試方法不止這一種，還有很多種方法，下面小編給大家分享了幾種方法，具體內容請往下看：
準備環境
啟動一個web服務器，提供端口.
[wyq@localhost ~]$ python -m SimpleHTTPServer 8080
Serving HTTP on 0.0.0.0 port 8080 ...
用其它web服務器提供端口也一樣，由于python比較方便，這里就用它
1、使用telnet判斷
telnet是windows標準服務，可以直接用；如果是linux機器，需要安裝telnet.
用法: telnet ip port
1）先用telnet連接不存在的端口
[root@localhost ~]# telnet 10.0.250.3 80
Trying 10.0.250.3...
telnet: connect to address 10.0.250.3: Connection refused #直接提示連接被拒絕
2）再連接存在的端口
[root@localhost ~]# telnet localhost 22
Trying ::1...
Connected to localhost. #看到Connected就連接成功了
Escape character is '^]'.
SSH-2.0-OpenSSH_5.3
a
Protocol mismatch.
Connection closed by foreign host.
2、使用ssh判斷
ssh是linux的標準配置并且最常用，可以用來判斷端口嗎？
用法: ssh -v -p port username@ip
-v 調試模式(會打印日志).
-p 指定端口
username可以隨意
1）連接不存在端口
[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）連接存在的端口
[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選項也可以咯
3、使用wget判斷
wget是linux下的下載工具，需要先安裝.
用法: wget ip:port
1）連接不存在的端口
[root@localhost ~]# wget ...:
---- ::-- http://.../
Connecting to ...:... failed: Connection refused.
2）連接存在的端口
[root@localhost ~]# wget ...:
---- ::-- http://...:/
Connecting to ...:... connected.
HTTP request sent, awaiting response...
4、使用端口掃描工具
[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
總結
提供端口服務，則使用了tcp協議，上面是以web服務器為例。如果服務器是更簡單的tcp服務器，三個工具同樣適用.
三個工具的共同點是：1.以tcp協議為基礎；2.能訪問指定端口. 遵循這兩點可以找到很多工具.
一般在windows下使用telnet比較方便，linux下個人就比較喜歡用wget.
