IPMonitor Component

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The IPMonitor class allows applications to monitor network packets on multiple platforms.

Syntax

pcapfilter.IPMonitor

Remarks

IPMonitor is a lightweight struct that allows applications to monitor network activity across multiple platforms, including Windows, Linux, and macOS. It utilizes the "libpcap" library and underlying network drivers to capture and report network packets in real-time. The struct provides the ability to capture individual network packets for detailed analysis, or collect aggregated packet statistics for monitoring network performance.

Setup

Before using the struct, a libpcap-compatible network library must be installed on the system. For detailed installation instructions, please refer to the Network Filter Library section. This setup only needs to be done once.

Linux and macOS

For Linux and macOS systems, permissions may need to be adjusted as described in the System Configuration in Linux and macOS instructions page to allow the application to capture packets.

Retrieving Network Adapters

The first step in using the struct is to identify the name of the network adapter that will be monitored. To retrieve the list of network adapters available on the system, call the ListAdapters method. Once the method is called, the adapters will be accessible via the Adapters property.

// Retrieve the list of network adapters available on the system ipmonitor.ListAdapters(); // Display the available adapters foreach (Adapter adapter in ipmonitor.Adapters) { Console.WriteLine($"Adapter Name: {adapter.Name}"); Console.WriteLine($"Description: {adapter.Description}"); }

Packet Filters

Before starting to monitor a network adapter, filters can be applied to capture only the packets that match certain criteria.

The Direction property can be used to specify whether to capture incoming packets, outgoing packets, or both. In addition to directionality, the Filter property can be set to a pcap filter expression string that allows for filtering based on IP addresses, protocol types, ports, and more. For more information on supported filter expressions, please see the pcap-filter(7) man page. // Only capture incoming packets ipmonitor.Direction = callback.PCAPFilter.Constants.PACKET_DIRECTION_INCOMING; // Only capture TCP packets from IP 192.168.1.1 on port 80 ipmonitor.Filter = "src host 192.168.1.1 and tcp port 80";

Operation Modes

In addition to packet filters, the struct supports multiple operation modes that determine what kind of packet information will be reported.

Capture Mode

Setting the OperationMode property to PCAP_MODE_CAPT will cause the struct to capture individual network packets and report them through the Packet event. // Capture individual packet information ipmonitor.OperationMode = (int)OperationModes.PCAP_MODE_CAPT;

Statistical Mode

Setting the OperationMode property to PCAP_MODE_STAT will instead cause the struct to collect aggregated packet statistics and report them through the Statistics event. // Report aggregated packet statistics ipmonitor.OperationMode = (int)OperationModes.PCAP_MODE_STAT;

Monitoring an Adapter

After configuring the filters and operation mode, start monitoring the network adapter by calling the Activate method and specifying the adapter name.

// Get the name of the first adapter returned by ListAdapters() ipmonitor.ListAdapters(); string adapterToMonitor = ipmonitor.Adapters[0].Name; // Start monitoring the adapter ipmonitor.Activate(adapterToMonitor);

Retrieving Packet Information

Depending on the current OperationMode, packet information is retrieved differently. In both modes, the DoEvents method must be called to prompt the struct to fire events and report packet information.

Capture Mode:

In capture mode, calling DoEvents will cause the struct to process any packets captured by the struct and fire the Packet for each one. ipmonitor.OnPacket += (s, e) => { // Print out information about each individual packet Console.WriteLine($"Packet captured at {e.TimeStamp}"); Console.WriteLine($"Packet Size: {e.PacketSize} bytes"); };

Statistical Mode:

In statistical mode, calling DoEvents will prompt the struct to collect packet statistics and report them through the Statistics event. ipmonitor.OnStatistics += (s, e) => { // Print out packet statistics Console.WriteLine($"Statistics collected at {e.TimeStamp}"); Console.WriteLine($"Packets Captured: {e.CapturedPackets}"); Console.WriteLine($"Bytes Captured: {e.CapturedBytes}"); };

Capture Statistics

Regardless of the current OperationMode, cumulative statistics about the packets captured since monitoring began can be retrieved by calling the GetStatistics method. long receivedPackets = 0; // The number of packets received since monitoring began long droppedPackets = 0; // The number of packets dropped by the component since monitoring began long adapterDroppedPackets = 0; // The number of packets dropped by the adapter since monitoring began ipmonitor.GetStatistics(ref receivedPackets, ref droppedPackets, ref adapterDroppedPackets); Console.WriteLine($"Packets Received: {receivedPackets}"); Console.WriteLine($"Packets Dropped: {droppedPackets}"); Console.WriteLine($"Packets Dropped by Adapter: {adapterDroppedPackets}");

Deactivating Monitoring

To stop monitoring the adapter and cease reporting packets, call the Deactivate method. ipmonitor.Deactivate();

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.

Active Property (IPMonitor Component)

Indicates whether the class is active and monitoring network traffic.

Syntax

func (obj *IPMonitor) Active() (bool, error)

Default Value

false

Remarks

This property reflects whether the struct is actively monitoring network traffic. It is automatically set to true after a successful call to Activate, and to false when monitoring is stopped with the Deactivate method.

This property is read-only.

Data Type

bool

AdapterCount Property (IPMonitor Component)

The number of records in the Adapter arrays.

Syntax

func (obj *IPMonitor) AdapterCount() (int32, error)

Default Value

0

Remarks

This property controls the size of the following arrays:

• AdapterDescription
• AdapterName

The array indices start at 0 and end at AdapterCount - 1.

This property is read-only.

Data Type

int32

AdapterDescription Property (IPMonitor Component)

Description of the adapter.

Syntax

func (obj *IPMonitor) AdapterDescription(AdapterIndex int32) (string, error)

Default Value

""

Remarks

Description of the adapter.

The AdapterIndex parameter specifies the index of the item in the array. The size of the array is controlled by the AdapterCount property.

This property is read-only.

Data Type

string

AdapterName Property (IPMonitor Component)

The name of the adapter.

Syntax

func (obj *IPMonitor) AdapterName(AdapterIndex int32) (string, error)

Default Value

""

Remarks

The name of the adapter. This value can be passed into the Activate method to start monitoring the adapter.

The AdapterIndex parameter specifies the index of the item in the array. The size of the array is controlled by the AdapterCount property.

This property is read-only.

Data Type

string

Direction Property (IPMonitor Component)

Specifies the direction of packets to capture.

Syntax

func (obj *IPMonitor) Direction() (int32, error)
func (obj *IPMonitor) SetDirection(value int32) error

Default Value

0

Remarks

The property makes it possible to capture just outgoing or just incoming packets, working as a simple filter for the network packets. The property value can be one of the following:

Data Type

int32

Filter Property (IPMonitor Component)

Specifies filter criteria used to determine which network packets are captured.

Syntax

func (obj *IPMonitor) Filter() (string, error)
func (obj *IPMonitor) SetFilter(value string) error

Default Value

""

Remarks

This property specifies a filter expression string that determines which network packets are captured and reported. For additional filtering, the Direction property can be used to limit packet capture to incoming or outgoing traffic.

This property can be set before or after calling Activate to start monitoring. In some platforms, changing the value of this property while monitoring is active may result in some packets being dropped or reported even if they do not match the new filter rules. For more details on platform-specific behavior, please see the pcap-filter(7) man page.

Filter Expression Syntax

The filter expression follows the syntax used by libpcap. A filter takes the form of a series of conditions that specify the criteria packets must meet to be captured. Expressions can be combined using conjunctions and, or, and optionally preceded by not.

[not] condition [and|or [not] condition ... ]

For more comprehensive information on filter expressions, please refer to the pcap-filter(7) documentation. Below is a simplified overview of common filter expressions:

Example (Simple): // Only capture packets to and from IP 192.168.1.1 ipmonitor.Filter = "host 192.168.1.1";

Example (Advanced): // Only capture TCP packets from IP 192.168.1.1 on port 80 ipmonitor.Filter = "src host 192.168.1.1 and tcp port 80";

Data Type

string

OperationMode Property (IPMonitor Component)

Specifies the mode of operation.

Syntax

func (obj *IPMonitor) OperationMode() (int32, error)
func (obj *IPMonitor) SetOperationMode(value int32) error

Default Value

0

Remarks

This property determines the type of packet information to report when DoEvents is called. The property value can be one of the following:

Data Type

int32

Tag Property (IPMonitor Component)

This property stores application-defined data specific to a particular instance of the class.

Syntax

func (obj *IPMonitor) Tag() (int64, error)
func (obj *IPMonitor) SetTag(value int64) error

Default Value

0

Remarks

This property can be used to store data specific to a particular instance of the struct.

Data Type

int64

Activate Method (IPMonitor Component)

Starts monitoring network traffic.

Syntax

func (obj *IPMonitor) Activate(Adapter string) error

Remarks

This method enables monitoring network packets on a specified network adapter. To disable monitoring, call Deactivate instead.

When this method is called, the struct will begin monitoring the specified adapter for network activity. Packets will be captured and reported differently depending on the value of the OperationMode property. Once monitoring is active, the Active property will be automatically set to true.

Adapter specifies the name of the network adapter to monitor. The list of available adapters can be obtained via the ListAdapters method.

Packet Reporting

When Active is set to true, the struct will report packet information based on the value of the OperationMode property. The following operation modes determine how packets are processed and reported:

Config Method (IPMonitor Component)

Sets or retrieves a configuration setting.

Syntax

func (obj *IPMonitor) Config(ConfigurationString string) (string, error)

Remarks

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

These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the struct, 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.

Deactivate Method (IPMonitor Component)

Stops monitoring network traffic.

Syntax

func (obj *IPMonitor) Deactivate() error

Remarks

This method stops monitoring network traffic. Once called, the struct will cease capturing packets and the Active property will be automatically set to false.

DoEvents Method (IPMonitor Component)

Processes events from the internal message queue.

Syntax

func (obj *IPMonitor) DoEvents() error

Remarks

This method processes events from the internal message queue and fires the corresponding events based on the current OperationMode. It should be called periodically to prompt the struct to fire events and report packet information.

Capture Modes

This method behaves differently depending on the value of the OperationMode property.

When OperationMode is set to PCAP_MODE_CAPT, calling this method while monitoring is active will prompt the struct to process any packets captured since the last call and fire the Packet event for each one. If there are no new packets to report, the method will wait for a duration specified by the PacketTimeout configuration setting before returning.

If OperationMode is set to PCAP_MODE_STAT, calling this method will instead tell the struct to collect packet statistics since the last call and fire the Statistics event with the aggregated data.

GetStatistics Method (IPMonitor Component)

Retrieves the total number of packets received and dropped since monitoring began.

Syntax

func (obj *IPMonitor) GetStatistics(Received *int64, Dropped *int64, AdapterDropped *int64) error

Remarks

This method provides capture statistics about the packets monitored by the struct and the underlying driver since Activate was called to start monitoring.

The Received parameter provides the number of packets received since monitoring began.

The Dropped parameter provides the number of packets that were dropped since monitoring began. Packets may be dropped if BufferSize is too small to keep all of the data, or because DoEvents was called too infrequently.

The AdapterDropped parameter provides the full number of packets that were dropped by the network adapter since monitoring began.

Platform Differences

This method is platform-dependent. It uses the underlying pcap_stats() function from the libpcap library to retrieve packet statistics, which may cause the values provided in the Received, Dropped, and AdapterDropped parameters to differ depending on the platform.

• Received: On some platforms, this count may include all packets, regardless of whether they matched the filter criteria set using Filter.
• Dropped: This value may not be available on all platforms.
• AdapterDropped: This count might not be implemented on some platforms. If its value is 0, it could indicate either no drops or that the statistic is unavailable.

For more information regarding platform differences, please see the pcap_stats() documentation.

ListAdapters Method (IPMonitor Component)

Retrieves the network adapters available for monitoring.

Syntax

func (obj *IPMonitor) ListAdapters() error

Remarks

This method populates the Adapters collection with a list of network adapters available for monitoring. Each adapter in the collection includes a name and description provided by the network driver.

This method can be used to obtain the name of a network adapter before calling Activate to start monitoring it.

Example: // Populate the 'Adapters' collection with the list of available network adapters ipmonitor.ListAdapters(); // Start monitoring the first adapter in the collection ipmonitor.Activate(ipmonitor.Adapters[0].Name);

Error Event (IPMonitor Component)

This event fires if an unhandled error occurs during an event.

Syntax

// IPMonitorErrorEventArgs carries the IPMonitor Error event's parameters.
type IPMonitorErrorEventArgs struct {...}

func (args *IPMonitorErrorEventArgs) ErrorCode() int32
func (args *IPMonitorErrorEventArgs) Description() string
// IPMonitorErrorEvent defines the signature of the IPMonitor Error event's handler function.
type IPMonitorErrorEvent func(sender *IPMonitor, args *IPMonitorErrorEventArgs)

func (obj *IPMonitor) GetOnErrorHandler() IPMonitorErrorEvent
func (obj *IPMonitor) SetOnErrorHandler(handlerFunc IPMonitorErrorEvent)

Remarks

This event fires if an unhandled error occurs during another event. Developers can use this information to track down unhandled errors in an application's event handlers.

Packet Event (IPMonitor Component)

Fires when a network packet is captured.

Syntax

// IPMonitorPacketEventArgs carries the IPMonitor Packet event's parameters.
type IPMonitorPacketEventArgs struct {...}

func (args *IPMonitorPacketEventArgs) TimeStamp() time.Time
func (args *IPMonitorPacketEventArgs) PacketSize() int32
func (args *IPMonitorPacketEventArgs) Data() []byte
func (args *IPMonitorPacketEventArgs) DataSize() int32
// IPMonitorPacketEvent defines the signature of the IPMonitor Packet event's handler function.
type IPMonitorPacketEvent func(sender *IPMonitor, args *IPMonitorPacketEventArgs)

func (obj *IPMonitor) GetOnPacketHandler() IPMonitorPacketEvent
func (obj *IPMonitor) SetOnPacketHandler(handlerFunc IPMonitorPacketEvent)

Remarks

This event fires for each packet received from the monitored network adapter. The event will only fire if OperationMode is set to PCAP_MODE_CAPT and the captured packet matches the filter criteria specified in Filter and Direction. Packets are reported in the order they are received from the network adapter.

The Timestamp parameter contains the time when the packet was received by the network adapter.

The PacketSize parameter contains the total size of the packet as received by the network adapter. This represents the full byte size of the packet, which may be larger than the amount of data captured in the Data parameter.

The Data parameter contains the packet data that was captured. The amount of data captured is controlled by the MaxPacketSize configuration setting, and it may be smaller than the full packet size.

The DataSize parameter provides the size of the data contained in the Data parameter. This value represents how much of the packet data was actually captured and made available.

Packet Reporting

When Active is set to true, the struct will report packet information based on the value of the OperationMode property. The following operation modes determine how packets are processed and reported:

Statistics Event (IPMonitor Component)

Fires to provide aggregated packet statistics.

Syntax

// IPMonitorStatisticsEventArgs carries the IPMonitor Statistics event's parameters.
type IPMonitorStatisticsEventArgs struct {...}

func (args *IPMonitorStatisticsEventArgs) TimeStamp() time.Time
func (args *IPMonitorStatisticsEventArgs) CapturedPackets() int64
func (args *IPMonitorStatisticsEventArgs) CapturedBytes() int64
// IPMonitorStatisticsEvent defines the signature of the IPMonitor Statistics event's handler function.
type IPMonitorStatisticsEvent func(sender *IPMonitor, args *IPMonitorStatisticsEventArgs)

func (obj *IPMonitor) GetOnStatisticsHandler() IPMonitorStatisticsEvent
func (obj *IPMonitor) SetOnStatisticsHandler(handlerFunc IPMonitorStatisticsEvent)

Remarks

This event fires to provide aggregated packet statistics collected from the network adapter. The event will only fire if OperationMode is set to PCAP_MODE_STAT. Calling DoEvents while monitoring is active will prompt the struct to report packet statistics and fire this event.

The TimeStamp parameter contains the time when the packet statistics were collected.

The CapturedPackets parameter contains the number of packets captured since the last time the event was fired.

The CapturedBytes parameter contains the total byte size of the packets captured since the last time the event was fired.

Packet Reporting

When Active is set to true, the struct will report packet information based on the value of the OperationMode property. The following operation modes determine how packets are processed and reported:

Config Settings (IPMonitor Component)

The struct 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 struct, access to these internal properties is provided through the Config method.

IPMonitor Config Settings

Base Config Settings

Trappable Errors (IPMonitor Component)