使用调试侦听端口启动进程内JVM。 如何检查端口是否繁忙

Question

I use the function JNI_CreateJavaVM to create, on windows, an in-process JVM into an executable. I also pass some options to turn on debugging, in particular:

-Xrunjdwp:transport=dt_socket,server=y,address=666,suspend=n

along with some other options. This works fine .

The problem I have though is if I start two versions of the executable: JNI_CreateJavaVM crashes. The obvious fix is to check if port 666 is busy and, if so, use a different port number. Except I don't know how to do this!

So, my question: how can I check if a port is being listened on already?

Answer 1

Don't test for port-in-use in advance. Just let your application do what it wants to do, and catch the exception there. The situation can change between the time you test and when you actually try to use the port.

Furthermore, if you are trying to write a server application, you can have the operating system automatically pick a free port for you. From the JavaDoc for http://docs.oracle.com/javase/7/docs/api/java/net/ServerSocket.html

Creates a server socket, bound to the specified port. A port number of 0 means that the port number is automatically allocated, typically from an ephemeral port range. This port number can then be retrieved by calling getLocalPort.