解决办法，重启机器
可能是我以前用的jenkins url 是127.0.0.1 然后是缓存什么没有释放掉所致
<jnlp codebase="http://183.62.104.48:8081/computer/win12/" spec="1.0+"><information><title>Agent for win12</title><vendor>Jenkins project</vendor><homepage href="https://jenkins-ci.org/"/></information><security><all-permissions/></security><resources><j2se java-vm-args="-Xrs -Xmx256m" version="1.7+"/><jar href="http://183.62.104.48:8081/jnlpJars/remoting.jar"/><property name="hudson.showWindowsServiceInstallLink" value="true"/></resources><application-desc main-class="hudson.remoting.jnlp.Main"><argument>9a7f3c0e8bed2742eceba49eb806327b88085f973bf782e231ccc061bee4ddf5</argument>
<argument>win12</argument><argument>-tunnel</argument><argument>127.0.0.1:8080</argument><argument>-url</argument><argument>http://183.62.104.48:8081/</argument></application-desc></jnlp>