TraceRoute Component

Properties   Methods   Events   Config Settings   Errors  

The TraceRoute component allows you to trace the path that the IP packets take on the Internet.

Syntax

TipwTraceRoute

Remarks

The component implements a standard IP TraceRoute as defined in RFC 1393.

To use the component, simply call the TraceTo method and set the Host parameter to the domain name or IP address of the host you want to trace the path to. This is identical to setting the RemoteHost property to the domain name or IP address. The component will start sending probe packets toward the host, and as it receives replies, it will fire Hop events giving information about the route. The same information is also provided in the Hops properties.

The ResolveNames property enables or disables DNS resolution of IP addresses received during the trace. If set to False, only IP addresses are provided. If set to True, the component will attempt to resolve the names of the hosts in the route. This may considerably increase the time it takes to complete the trace.

The HopTimeout property determines the maximum waiting time for a response in each hop of the trace, while the Timeout property defines the maximum waiting time for the whole trace. The HopLimit property specifies the maximum number of hops allowed for a trace.

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.

HopLimit Property (TraceRoute Component)

This property includes the maximum number of hops to allow for a trace.

Syntax

property HopLimit: Integer read get_HopLimit write set_HopLimit;

Default Value

64

Remarks

This property is used to limit lengthy traces. A value of 0 indicates an unbounded trace.

Note: If the value of Timeout is 0, an unbounded trace may cause a call to TraceTo to block indefinitely. To cancel such a route trace, call Interrupt.

Hops Property (TraceRoute Component)

This property includes a collection of hops to the RemoteHost .

Syntax

property Hops: TipwTraceHopList read get_Hops;

Remarks

This property shows the hops as the trace progresses toward the final destination (RemoteHost). Each hop is defined by a TraceHop type.

This property is read-only.

Please refer to the TraceHop type for a complete list of fields.

HopTimeout Property (TraceRoute Component)

This property includes the maximum amount of time to wait for an individual hop to complete.

Syntax

property HopTimeout: Integer read get_HopTimeout write set_HopTimeout;

Default Value

10

Remarks

The time value is in seconds. If 0, HopTimeout will be ignored, and only the Timeout for the whole trace will be taken into account.

Idle Property (TraceRoute 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 (TraceRoute 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.

RemoteHost Property (TraceRoute Component)

This property includes the address of a host to trace to.

Syntax

property RemoteHost: String read get_RemoteHost write set_RemoteHost;

Default Value

''

Remarks

Traces are initiated by setting RemoteHost to the name or address of the host to trace to.

This property must contain a valid Internet domain name or address or an error will be returned.

To interrupt a trace in progress, set RemoteHost to empty string.

Example. Perform a TraceRoute:

TraceRouteControl.TraceTo("myHost") is equivalent to TraceRouteControl.RemoteHost = "myHost"

ResolveNames Property (TraceRoute Component)

This property determines whether the component resolves the host name for each host during the trace.

Syntax

property ResolveNames: Boolean read get_ResolveNames write set_ResolveNames;

Default Value

false

Remarks

This property determines whether the component resolves the name of host at each "hop" during the trace. The default value is False.

Note: If this property is set to True, the trace takes longer because of name resolution.

Timeout Property (TraceRoute 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.

Config Method (TraceRoute 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 (TraceRoute 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.

Interrupt Method (TraceRoute 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 (TraceRoute Component)

This method will reset the component.

Syntax

procedure Reset();

Remarks

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

ResolveRemoteHost Method (TraceRoute Component)

This method resolves the hostname in RemoteHost to an IP address.

Syntax

procedure ResolveRemoteHost();

Remarks

This method resolves the hostname specified by RemoteHost to an IP address. The resolved value is available in the RemoteHost property after this method returns.

In most cases, calling this method is not necessary; the component will resolve the hostname automatically when needed. If DelayHostResolution is True, this method may be called to manually resolve RemoteHost, if desired.

TraceTo Method (TraceRoute Component)

This method traces the route to a host.

Syntax

procedure TraceTo(Host: String);

Remarks

Traces are initiated by calling TraceTo, with the Host argument set to the name or address of the destination host to trace to. Host must contain a valid Internet domain name or address, or the component raises an exception. To interrupt a trace in progress, set RemoteHost to empty string. Calling this method is equivalent to setting the RemoteHost property to Host.

Example. Perform a TraceRoute:

TraceRouteControl.TraceTo("myHost") is equivalent to TraceRouteControl.RemoteHost = "myHost"

Error Event (TraceRoute 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.

Hop Event (TraceRoute Component)

This event is fired for each hop in the trace to the RemoteHost .

Syntax

type THopEvent = procedure (
  Sender: TObject;
  HopNumber: Integer;
  const HostAddress: String;
  Duration: Integer
) of Object;

property OnHop: THopEvent read FOnHop write FOnHop;

Remarks

This event provides access to the information for each hop in the trace. The HopNumber parameter denotes which hop the trace is at. The HostAddress parameter is the IP address of the host for the hop identified by HopNumber. The Duration parameter shows the amount of time taken by the hop.

HopResolved Event (TraceRoute Component)

This event is fired when the name of a hop address is found.

Syntax

type THopResolvedEvent = procedure (
  Sender: TObject;
  HopNumber: Integer;
  StatusCode: Integer;
  const HopHostName: String
) of Object;

property OnHopResolved: THopResolvedEvent read FOnHopResolved write FOnHopResolved;

Remarks

The StatusCode contains 0 if the address is resolved successfully, or an error code, in which case, HopHostName contains a textual description of the error.

Host name resolution is disabled by default. Set ResolveNames to True to enable it.

TraceHop Type

The type describes a hop in the route to the destination.

Remarks

This type describes a hop that exists in the route to the destination specified by the RemoteHost property. This type contains fields denoting the HostAddress, HostName, Time, ErrorCode, and ErrorDescription.

Fields

Constructors

constructor Create();

Config Settings (TraceRoute 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.

TraceRoute Config Settings

ICMP Config Settings

Socket Config Settings

Base Config Settings

Trappable Errors (TraceRoute Component)

TraceRoute Errors

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

ICMP Errors

SSL Errors

TCP/IP Errors