class SocketUtils: Simple utility methods for working with network sockets — for example, for finding available ports on {@code localhost}. Within this class, a TCP port refers to a port for a {@link Server socket }; whereas, a UDP port refers to a port for a {@link DatagramSocket} 简单的工具方法，用来检查TCP/UDP network sockets的某数字段的可用端口；
public class SocketUtils {
…
private enum SocketType {
TCP {
@ Override
protected boolean isPortAvailable(int port) {
try {
ServerSocket serverSocket = ServerSocketFactory.getDefault().createServerSocket(
port, 1, InetAddress.getByName(” localhost “));
serverSocket. close ();
return true;
}
catch (Exception ex) {
return false;
}
}
},
UDP {
@Override
protected boolean isPortAvailable(int port) {
try {
Datagram Socket socket = new DatagramSocket(port, InetAddress.getByName(“localhost”));
socket.close();
return true;
}
catch (Exception ex) {
return false;
}
}
};
….
}
从以上代码中可用看出，org. Spring framework.util.socketUtils就是对socket的一种简单扩展，与socket有关的两个库 java .net, javax .net，像上面code里有用到java.net.ServerSocket和 javax.net.ServerSocketFactory对象。
对这两个对象一直追踪，发现最后到了这里：
JAVA UDP 底层
JAVA TCP 底层
对，最后的方法都是Native级的, 所以，可以看出，Java.net和javax.net其实也只是对Socket 加壳 封装，真正的Socket应该在C级了
