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()

Method Summary

Modifier and Type	Method	Description
TimeInfo	getTime(InetAddress host)	Retrieves the time information from the specified server on the default NTP port and returns it.
TimeInfo	getTime(InetAddress host, int port)	Retrieves the time information from the specified server and port and returns it.
int	getVersion()	Returns the NTP protocol version number that client sets on request packet that is sent to remote host (e.g.
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()

Method Details

getTime

public TimeInfo getTime(InetAddress host)
                 throws IOException

Retrieves 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

Retrieves 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()

Returns 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