54 lines
1.2 KiB
Markdown
54 lines
1.2 KiB
Markdown
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# Telnet 测试端口连通性
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telnet命令是TELNET协议的用户接口，它支持两种模式：命令模式和会话模式，虽然telnet支持许多命令，但大部分情况下，我们只是使用它查看目标主机是否打开了某端口（默认是23）。
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其执行结果有两种：
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## 端口未打开
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```bash
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telnet 101.199.97.65 62715
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Trying 101.199.97.65...
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telnet: connect to address 101.199.97.65: Connection refused
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```
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此时，命令已退出。
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## 端口已打开
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```bash
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telnet 101.199.97.65 62715
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Trying 101.199.97.65...
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Connected to 101.199.97.65.
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Escape character is '^]'.
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```
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此时命令未退出。
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根据提示Escape character is '^]'.可知退出字符为'^]'（CTRL+]）。此时输入其它字符不能使其退出，CTRL+C都不行。输入CTRL+]后会自动执行，进入命令模式：
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```bash
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^]
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telnet>
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```
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此时再运行 quit 才会真正退出。
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```bash
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telnet> quit
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Connection closed.
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```
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其中，Escape character 可以自定义，使用参数 -e：
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```bash
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telnet -e p 101.199.97.65 62715 #使用p字符
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Telnet escape character is 'p'.
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Trying 101.199.97.65...
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Connected to 101.199.97.65.
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Escape character is 'p'.
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p
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telnet> quit
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Connection closed.
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```
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