| Grails Version: 3.1.4
| Groovy Version: 2.4.6
| JVM Version: 1.7.0_80
根据grails手册，可以通过以下方式指定端口，不过我发现无效哈！
grails -Dserver.port=8090 run-app
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解决方法：
| Enter a command name to run. Use TAB for completion:
grails> help run-app
| Command: run-app
| Description:
Runs a Grails application
| Usage:
grails run-app
| Flags:
* debug-jvm - Starts the JVM in debug mode allowing attachment of a remote debugger
* https - Starts Grails in HTTPS mode on port 8443
* port - Specifies the port which to start Grails on (defaults to 8080 or 8443 for HTTPS)
* host - Specifies the host to bind to
* verbose - Show more output from the build during startup
grails>
根据帮助命令help run-app的提示信息可知，port用于指定端口，于是，我试了一下：
run-app --port=80
竟然成功了哈。。。