apache使用proxypass连接tomcat 的一个问题 error(120006)

apache使用proxypass连接tomcat 的一个问题，apache的error log片段如下

我使用apache管理了多个tomcat，每个tomcat都使用不同的端口，其他网站都可以正常访问，但是今天新增了一个就出现这个问题，非常奇怪

[Wed Mar 09 11:19:50 2011] [error] ajp_read_header: ajp_ilink_receive failed
[Wed Mar 09 11:19:50 2011] [error] (120006)APR does not understand this error code: proxy: read response failed from (null) (localhost)
[Wed Mar 09 11:19:53 2011] [error] (70014)End of file found: ajp_ilink_receive() can't receive header
[Wed Mar 09 11:19:53 2011] [error] ajp_read_header: ajp_ilink_receive failed
[Wed Mar 09 11:19:53 2011] [error] (120006)APR does not understand this error code: proxy: read response failed from (null) (localhost)
[Wed Mar 09 11:19:53 2011] [error] (70014)End of file found: ajp_ilink_receive() can't receive header
[Wed Mar 09 11:19:53 2011] [error] ajp_read_header: ajp_ilink_receive failed
[Wed Mar 09 11:19:53 2011] [error] (120006)APR does not understand this error code: proxy: read response failed from (null) (localhost)
[Wed Mar 09 11:19:54 2011] [error] (70014)End of file found: ajp_ilink_receive() can't receive header
[Wed Mar 09 11:19:54 2011] [error] ajp_read_header: ajp_ilink_receive failed

 在网上搜了很多方法，都是不能解决问题，后来经过排查，发现和 ajp的端口有关系，原来使用的是8009，修改为大于8010的端口即可，问题解决了，但是不知道原因，希望对遇到相同问题的朋友们有帮助，或者有人知道原因，请分享一下