Package org.apache.commons.net.ntp

# Class NTPUDPClient

java.lang.Object
org.apache.commons.net.DatagramSocketClient
org.apache.commons.net.ntp.NTPUDPClient

All Implemented Interfaces:
  `AutoCloseable`

public final class NTPUDPClient extends DatagramSocketClient
The NTPUDPClient class is a UDP implementation of a client for the Network Time Protocol (NTP) described in RFC 1305 as well as the Simple Network Time Protocol (SNTP) in RFC-2030. To use the class, merely open a local datagram socket with open and call getTime to retrieve the time. Then call close to close the connection properly. Successive calls to getTime are permitted without re-establishing a connection. That is because UDP is a connectionless protocol and the Network Time Protocol is stateless.

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `static final int`
  `DEFAULT_PORT`
  The default NTP port.

  ### Fields inherited from class org.apache.commons.net.DatagramSocketClient

  `_isOpen_, _socket_, _socketFactory_, _timeout_`

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `NTPUDPClient()`
  Constructs a new instance.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `TimeInfo`
  `getTime(InetAddress host)`
  Gets the time information from the specified server on the default NTP port and returns it.
  `TimeInfo`
  `getTime(InetAddress host, int port)`
  Gets the time information from the specified server and port and returns it.
  `int`
  `getVersion()`
  Gets the NTP protocol version number that client sets on request packet that is sent to remote host (e.g. 3=NTP v3, 4=NTP v4, etc.)
  `void`
  `setVersion(int version)`
  Sets the NTP protocol version number that client sets on request packet communicate with remote host.

  ### Methods inherited from class org.apache.commons.net.DatagramSocketClient

  `checkOpen, close, getCharset, getCharsetName, getDefaultTimeout, getLocalAddress, getLocalPort, getSoTimeout, getSoTimeoutDuration, isOpen, open, open, open, setCharset, setDatagramSocketFactory, setDefaultTimeout, setDefaultTimeout, setSoTimeout, setSoTimeout`

  ### Methods inherited from class java.lang.Object

  `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Field Details

  - ### DEFAULT_PORT

    public static final int DEFAULT_PORT
    The default NTP port. It is set to 123 according to RFC 1305.
    See Also:
      - Constant Field Values

- ## Constructor Details

  - ### NTPUDPClient

    public NTPUDPClient()
    Constructs a new instance.

- ## Method Details

  - ### getTime

    public TimeInfo getTime(InetAddress host) throws IOException
    Gets the time information from the specified server on the default NTP port and returns it. The time is the number of milliseconds since 00:00 (midnight) 1 January 1900 UTC, as specified by RFC 1305. This method reads the raw NTP packet and constructs a TimeInfo object that allows access to all the fields of the NTP message header.
    Parameters:
      `host` - The address of the server.
    Returns:
      The time value retrieved from the server.
    Throws:
      `IOException` - If an error occurs while retrieving the time.

  - ### getTime

    public TimeInfo getTime(InetAddress host, int port) throws IOException
    Gets the time information from the specified server and port and returns it. The time is the number of milliseconds since 00:00 (midnight) 1 January 1900 UTC, as specified by RFC 1305. This method reads the raw NTP packet and constructs a TimeInfo object that allows access to all the fields of the NTP message header.
    Parameters:
      `host` - The address of the server.
      `port` - The port of the service.
    Returns:
      The time value retrieved from the server.
    Throws:
      `IOException` - If an error occurs while retrieving the time or if received packet does not match the request.

  - ### getVersion

    public int getVersion()
    Gets the NTP protocol version number that client sets on request packet that is sent to remote host (e.g. 3=NTP v3, 4=NTP v4, etc.)
    Returns:
      the NTP protocol version number that client sets on request packet.
    See Also:
      - `setVersion(int)`

  - ### setVersion

    public void setVersion(int version)
    Sets the NTP protocol version number that client sets on request packet communicate with remote host.
    Parameters:
      `version` - the NTP protocol version number