NetClock Component

Properties   Methods   Events   Config Settings   Errors  

The NetClock component provides the current time in Greenwich Mean Time from an Internet Time Server.

Syntax

TipwNetClock

Remarks

The NetClock component implements a standard Time Protocol client as specified in RFC 868, as well as an SNTP (Simple Network Time Protocol).

The address of the Time Server is provided in the TimeServer property. You get the time by calling the GetTime method.

The component also allows you to synchronize your system time with that of the TimeServer. This is done through the GetAndSetTime method. Calling GetAndSetTime will request the time from the server and then set the system clock to match it.

Property List

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The following is the full list of the properties of the component with short descriptions. Click on the links for further details.

Method List

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The following is the full list of the methods of the component with short descriptions. Click on the links for further details.

Event List

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The following is the full list of the events fired by the component with short descriptions. Click on the links for further details.

Config Settings

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The following is a list of config settings for the component with short descriptions. Click on the links for further details.

Idle Property (NetClock Component)

The current status of the component.

Syntax

property Idle: Boolean read get_Idle;

Default Value

true

Remarks

This property will be False if the component is currently busy (communicating or waiting for an answer), and True at all other times.

This property is read-only.

LocalHost Property (NetClock Component)

The name of the local host or user-assigned IP interface through which connections are initiated or accepted.

Syntax

property LocalHost: String read get_LocalHost write set_LocalHost;

Default Value

''

Remarks

This property contains the name of the local host as obtained by the gethostname() system call, or if the user has assigned an IP address, the value of that address.

In multihomed hosts (machines with more than one IP interface) setting LocalHost to the IP address of an interface will make the component initiate connections (or accept in the case of server components) only through that interface. It is recommended to provide an IP address rather than a hostname when setting this property to ensure the desired interface is used.

If the component is connected, the LocalHost property shows the IP address of the interface through which the connection is made in internet dotted format (aaa.bbb.ccc.ddd). In most cases, this is the address of the local host, except for multihomed hosts (machines with more than one IP interface).

Note: LocalHost is not persistent. You must always set it in code, and never in the property window.

LocalTime Property (NetClock Component)

This property includes the time returned by the TimeServer converted to local time.

Syntax

property LocalTime: String read get_LocalTime;

Default Value

''

Remarks

The server provides Greenwich Mean Time (GMT). This property contains the corresponding local time formatted as "MM/DD/YYYY HH:MM:SS" (where "HH" is in 24-hour format).

This property is read-only and not available at design time.

Protocol Property (NetClock Component)

This property is the protocol used by the component.

Syntax

property Protocol: TipwTProtocols read get_Protocol write set_Protocol;

TipwTProtocols = (
  tpTime,
  tpSNTP
);

Default Value

tpSNTP

Remarks

This property is the protocol used by the component. This property is used to specify which protocol the component will use to connect to the server. By default, this property is tpSNTP (1). The Time Protocol may be selected by setting this property to tpTimeProtocol (0).

ServerTime Property (NetClock Component)

This property includes the time returned by the TimeServer .

Syntax

property ServerTime: String read get_ServerTime;

Default Value

''

Remarks

This property contains the time returned by the TimeServer. The time is given in Greenwich Mean Time (GMT) and is formatted as "MM/DD/YYYY HH:MM:SS GMT" (where "HH" is in 24-hour format).

For the corresponding local time, please consult the LocalTime property.

This property is read-only and not available at design time.

Timeout Property (NetClock Component)

The timeout for the component.

Syntax

property Timeout: Integer read get_Timeout write set_Timeout;

Default Value

60

Remarks

If the Timeout property is set to 0, all operations will run uninterrupted until successful completion or an error condition is encountered.

If Timeout is set to a positive value, the component will wait for the operation to complete before returning control.

The component will use DoEvents to enter an efficient wait loop during any potential waiting period, making sure that all system events are processed immediately as they arrive. This ensures that the host application does not freeze and remains responsive.

If Timeout expires, and the operation is not yet complete, the component raises an exception.

Note: By default, all timeouts are inactivity timeouts, that is, the timeout period is extended by Timeout seconds when any amount of data is successfully sent or received.

The default value for the Timeout property is 60 seconds.

TimePort Property (NetClock Component)

This property includes the User Datagram Protocol (UDP) port where the remote time server is listening.

Syntax

property TimePort: Integer read get_TimePort write set_TimePort;

Default Value

123

Remarks

This property is the UDP port on the TimeServer to which time requests are sent. If Protocol is set to tpTimeProtocol, the component will set this property to 37.

This property is not available at design time.

TimeServer Property (NetClock Component)

This property includes the time server from which to request the time.

Syntax

property TimeServer: String read get_TimeServer write set_TimeServer;

Default Value

'pool.ntp.org'

Remarks

This property contains the time server from which to request the time. This property should be set to a valid internet address of a time server. The server will reply with its current time (in Greenwich Mean Time).

When Protocol is set to SNTP another public server that may be used is "time.google.com".

Time requests are sent to port TimePort on the TimeServer.

Config Method (NetClock Component)

Sets or retrieves a configuration setting.

Syntax

function Config(ConfigurationString: String): String;

Remarks

Config is a generic method available in every component. It is used to set and retrieve configuration settings for the component.

These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the component, access to these internal properties is provided through the Config method.

To set a configuration setting named PROPERTY, you must call Config("PROPERTY=VALUE"), where VALUE is the value of the setting expressed as a string. For boolean values, use the strings "True", "False", "0", "1", "Yes", or "No" (case does not matter).

To read (query) the value of a configuration setting, you must call Config("PROPERTY"). The value will be returned as a string.

DoEvents Method (NetClock Component)

This method processes events from the internal message queue.

Syntax

procedure DoEvents();

Remarks

When DoEvents is called, the component processes any available events. If no events are available, it waits for a preset period of time, and then returns.

GetAndSetTime Method (NetClock Component)

This method is the same as the GetTime method, but the system clock is also set to the received time.

Syntax

procedure GetAndSetTime();

Remarks

This method is similar to the GetTime method, but the system clock is also set to the received time (adjusted for timezone differences).

GetTime Method (NetClock Component)

This method sends a time request to the TimeServer to get the current time.

Syntax

procedure GetTime();

Remarks

This method sends a time request to the TimeServer on port 37. The reply is provided in the ServerTime property, and the equivalent local time is provided in the LocalTime property.

Interrupt Method (NetClock Component)

This method interrupts the current method.

Syntax

procedure Interrupt();

Remarks

If there is no method in progress, Interrupt simply returns, doing nothing.

Reset Method (NetClock Component)

This method resets the component.

Syntax

procedure Reset();

Remarks

This method will reset the component's properties to their default values.

Error Event (NetClock Component)

Fired when information is available about errors during data delivery.

Syntax

type TErrorEvent = procedure (
  Sender: TObject;
  ErrorCode: Integer;
  const Description: String
) of Object;

property OnError: TErrorEvent read FOnError write FOnError;

Remarks

The Error event is fired in case of exceptional conditions during message processing. Normally the component raises an exception.

The ErrorCode parameter contains an error code, and the Description parameter contains a textual description of the error. For a list of valid error codes and their descriptions, please refer to the Error Codes section.

Config Settings (NetClock Component)

The component accepts one or more of the following configuration settings. Configuration settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the component, access to these internal properties is provided through the Config method.

UDP Config Settings

Socket Config Settings

Base Config Settings

Trappable Errors (NetClock Component)

NetClock Errors

The component may also return one of the following error codes, which are inherited from other components.

UDP Errors

SSL Errors

TCP/IP Errors