Summary

DatagramPacket::getSocketAddress throws IllegalArgumentException if invoked on a packet whose address or port are not set, even though IllegalArgumentException is not specified.

Problem

The no-arg method DatagramPacket.getSocketAddress() is misleading, because it can throw an IllegalArgumentException even though it doesn't take any arguments. This can occur if the port of a DatagramPacket is not set before a call to getSocketAddress() is made.

Solution

In the recent fix for JDK-8236940, additional checks were added to ensure that a DatagramPacket cannot be sent to port 0. Following on from that fix, this issues changes the default port of a DatagramPacket from a value of -1 to 0. An IllegalArgumentException will therefore no longer be thrown from getSocketAddress(), when invoked on a packet that has not had its port explicitly set. Instead, an InetSocketAddress representing any local address with a port of 0 is returned.

The default values of the packets address and port are also specified.

Specification

     /**
      * Returns the IP address of the machine to which this datagram is being
-     * sent or from which the datagram was received.
+     * sent or from which the datagram was received, or {@code null} if not
+     * set.
      *
      * @return  the IP address of the machine to which this datagram is being
      *          sent or from which the datagram was received.
      * @see     java.net.InetAddress
      * @see #setAddress(java.net.InetAddress)
      */
     public synchronized InetAddress getAddress() {


     /**
      * Returns the port number on the remote host to which this datagram is
-     * being sent or from which the datagram was received.
+     * being sent or from which the datagram was received, or 0 if not set.
      *
      * @return  the port number on the remote host to which this datagram is
      *          being sent or from which the datagram was received.
      * @see #setPort(int)
      */
     public synchronized int getPort() {


     /**
-     * Gets the the SocketAddress (usually IP address + port number) of the remote
-     * host that this packet is being sent to or is coming from.
+     * Returns the {@link InetSocketAddress#InetSocketAddress(InetAddress, int)
+     * SocketAddress} (usually {@linkplain #getAddress() IP address} +
+     * {@linkplain #getPort() port number}) of the remote host that this packet
+     * is being sent to or is coming from.
      *
      * @return  the {@code SocketAddress}
      *
      * @since   1.4
      */
     public synchronized SocketAddress getSocketAddress() {