Java Bind Exception

问题:

What would cause a TCP socket to throw "java.net.BindException: Address already in use" even when reuse address is set to true? This only occurs if the application is quickly restarted. Running on CentOS 5 linux OS.

回答1:

This kinda explains it:

http://www.beej.us/guide/bgnet/output/html/singlepage/bgnet.html#bind

Sometimes, you might notice, you try to rerun a server and bind() fails, claiming "Address already in use." What does that mean? Well, a little bit of a socket that was connected is still hanging around in the kernel, and it's hogging the port. You can either wait for it to clear (a minute or so), or add code to your program allowing it to reuse the port, like this

(provides C code)

Basically, in C, you call a function called setsockopt(), and one of the parameters is called SO_REUSEADDR, which lets you reuse that port.

I found some brief links on google which should get you started figuring out how to set the equivalent option in Java:

http://java.sun.com/j2se/1.4.2/docs/guide/net/socketOpt.html

http://java.sun.com/j2se/1.4.2/docs/api/java/net/SocketOptions.html

回答2:

If what you say is correct you should be able to trap this exception in a loop and try again after a few seconds. (You shouldn't have to do this, but I have heard of a few odd things about CentOS)

回答3:

Java Bind Exception occurs If either of your port or InetAddress is already used and you want to use once again. So free up the port stop the program if running. otherwise change the port

Thanks Deepak