翻译自：
How to Test Port[TCP/UDP] Connectivity from a Linux Server (文档 ID 2212626.1)
适用于：
Linux OS - Version Oracle Linux 5.0 to Oracle Linux 6.8 [Release OL5 to OL6U8]
Information in this document applies to any platform.
目标：
在Linux服务器上检查TCP/UDP端口的连通性。
解决方案：
telnet和nc 是用来测试端口连通性的一般工具。
telnet可以测试tcp端口的连通性。
nc可以测试tcp和udp端口的连通性。
请确保telnet和nc工具已经安装

# yum install nc
# yum install telnet

测试tcp端口的连通性：
语法如下：

telnet <hostname/IP address> <port number>

如下是连通成功的例子：

# telnet 192.118.20.95 22
Trying 192.118.20.95...
Connected to 192.118.20.95.
Escape character is '^]'.
SSH-2.0-OpenSSH_6.6.1

Protocol mismatch.
Connection closed by foreign host.

如下是连通不成功的例子：

# telnet 192.118.20.95 22
Trying 192.118.20.95...
telnet: connect to address 192.118.20.95: No route to host

使用nc命令来测试tcp端口的连通性：
语法：

nc -z -v <hostname/IP address> <port number>

如下是连通成功的例子：

# nc -z -v 192.118.20.95 22
Connection to 192.118.20.95 22 port [tcp/ssh] succeeded!

如下是连通不成功的例子：

# nc -z -v 192.118.20.95 22
nc: connect to 192.118.20.95 port 22 (tcp) failed: No route to host

使用nc命令来测试udp端口的连通性：
语法：

nc -z -v -u <hostname/IP address> <port number>

# nc -z -v -u 192.118.20.95 123
Connection to 192.118.20.95 123 port [udp/ntp] succeeded!