ServerSocket getOption(SocketOption) in Java

getOption(SocketOption): This method is available in the java.net.ServerSocket class of Java.

Syntax:

Object java.net.ServerSocket.getOption(SocketOption<Object> name) throws IOException

This method takes one argument. This method returns the value of a socket option.

Type Parameters: <T> The type of the socket option value.

Parameters: One parameter is required for this method.

name: The socket option.

Returns: The value of the socket option.

Throws:

1. UnsupportedOperationException - if the server socket does not support the option.

2. IOException - if an I/O error occurs, or if the socket is closed.

3. NullPointerException - if the name is null.

4. SecurityException - if a security manager is set and if the socket option requires security permission and if the caller does not have the required permission. StandardSocketOptions do not require any security permission.

Approach 1: UnsupportedOperationException 

Java

package com.ServerSocket;

import java.io.IOException;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.SocketOption;

public class ServerSocketgetOption {
    public static void main(String[] args) throws IOException {

        int port = 8180, backlog = 15;
        InetAddress bindAddr = InetAddress.getLocalHost();
        ServerSocket serverSocket = new ServerSocket(port, backlog, bindAddr);
        SocketOption<Object> socketOptin = new SocketOption<Object>() {

            @Override
            public String name() {
                return "name";
            }

            @Override
            public Class<Object> type() {
                return null;
            }
        };
        serverSocket.getOption(socketOptin);

        serverSocket.close();
    }
}

Output:

Exception in thread "main" java.lang.UnsupportedOperationException: 'com.ServerSocket.ServerSocketgetOption$1@50cbc42f' not supported
	at java.base/sun.nio.ch.NioSocketImpl.getOption(NioSocketImpl.java:981)
	at java.base/java.net.ServerSocket.getOption(ServerSocket.java:1129)
	at com.ServerSocket.ServerSocketgetOption.main(ServerSocketgetOption.java:26)

Approach 2: NullPointerException 

Java

package com.ServerSocket;

import java.io.IOException;
import java.net.InetAddress;
import java.net.ServerSocket;

public class ServerSocketgetOption {
    public static void main(String[] args) throws IOException {

        int port = 8180, backlog = 15;
        InetAddress bindAddr = InetAddress.getLocalHost();
        ServerSocket serverSocket = new ServerSocket(port, backlog, bindAddr);

        serverSocket.getOption(null);

        serverSocket.close();
    }
}

Output:

Exception in thread "main" java.lang.NullPointerException
	at java.base/java.util.Objects.requireNonNull(Objects.java:208)
	at java.base/java.net.ServerSocket.getOption(ServerSocket.java:1126)
	at com.ServerSocket.ServerSocketgetOption.main(ServerSocketgetOption.java:14)

Some other methods of ServerSocket class

ServerSocket(): This method creates an unbound server socket.

ServerSocket(int): This method 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.

ServerSocket(int, int): This method creates a server socket and binds it to the specified local port number, with the specified backlog. 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.

ServerSocket(int, int, InetAddress): This method creates a server with the specified port, listens to the backlog, and local IP address to bind to. The bindAddr argument can be used on a multi-homed host for ServerSocket that will only accept connect requests to one of its addresses.

accept(): This method listens for a connection to be made to this socket and accepts it. The method blocks until a connection is made.

bind(SocketAddress): This method binds the ServerSocket to a specific address(IP address and port number).

bind(SocketAddress, int): This method binds the ServerSocket to a specific address.

close(): This method closes this socket. Any thread currently blocked in accept() will throw a SocketException.

getChannel(): This method returns the unique java.nio.channels.ServerSocketChannel object associated with this socket, if any.

getInetAddress(): This method returns the local address of this server socket.

getLocalPort(): This method returns the port number on which this socket is listening.

getLocalSocketAddress(): This method returns the address of the endpoint this socket is bound to.

getOption(SocketOption): This method returns the value of a socket option.

getReceiveBufferSize(): This method gets the value of the SO_RCVBUF option for this ServerSocket, which is the proposed buffer size that will be used for Sockets accepted from this ServerSocket.

getReuseAddress(): This method tests if SO_REUSEADDR is enabled.

getSoTimeout(): This method retrieves the setting for SO_TIMEOUT.0 returns implying that the option is disabled (i.e., timeout of infinity). 

isBound(): This method returns the binding state of the ServerSocket.

isClosed(): This method returns the closed state of the ServerSocket.

setOption(SocketOption, Object): This method sets the value of a socket option.

setPerformancePreferences(int, int, int): This method sets performance preferences for this ServerSocket.

setReceiveBufferSize(int): This method sets a default proposed value for the SO_RCVBUF option for sockets accepted from this ServerSocket.

setReuseAddress(boolean): This method enables/disables the SO_REUSEADDRsocket option. When a TCP connection is closed the connection may remain in a timeout state for a period of time after the connection is closed.

setSocketFactory(SocketImplFactory): This method sets the server socket implementation factory for the application.

setSoTimeout(int): This method enables/disables SO_TIMEOUT with the specified timeout, in milliseconds.

supportedOptions(): This method returns a set of the socket options supported by this server socket. This method will continue to return the set of options even after the socket has been closed.

toString(): This method returns the implementation address and implementation port of this socket as a String.