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IPWorks 2022 Android Edition

Version 22.0 [Build 8171]

MCast Component

Properties   Methods   Events   Configuration Settings   Errors  

The MCast component is used to multicast UDP datagrams to multicast capable hosts in multicast capable subnets. It can act both as a client and a server and communicate with any number of hosts simultaneously, as well as generate and receive broadcast packets.

Syntax

IPWorks.Mcast

Remarks

The MCast component is very similar to UDPPort, except for some additional properties that provide support for multicast datagrams. To send datagrams to a multicast group, simply assign the address of the group to RemoteHost. To receive datagrams from one or more groups, assign the group addresses to MulticastGroup one by one (after the component is activated. TimeToLive allows to specify how many subnets a packet should be allowed to receive. ReceiveInterface and SendInterface allow you to select the network interface for multicast operations.

The component is activated/deactivated through the Active property. This property enables or disables sends or receives. The data can be sent in the same way as UDPPort, by calling the Send method with a Text parameter or via the DataToSend property. The destination is specified using the RemoteHost and RemotePort properties. Inbound data is received through the DataIn event.

Property List


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

AcceptDataEnables or disables data reception (the DataIn event).
ActiveEnables or disables sending and receiving data.
LocalHostThe name of the local host or user-assigned IP interface through which connections are initiated or accepted.
LocalPortThe UDP port in the local host where MCast binds.
LoopbackEnables or disables loopback of data sent to the multicast group.
MulticastGroupMulticast group to join or leave.
ReceiveInterfaceThe interface with which to receive multicast packets. If empty, default is used.
RemoteHostThe address of the remote host (multicast group).
RemotePortThe UDP port in the remote host.
SendInterfaceThe interface from which multicast packets are sent. If empty, default is used.
TimeToLiveThe maximum number of subnets that a multicast datagram can traverse.

Method List


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

activateEnables sending and receiving data.
configSets or retrieves a configuration setting.
deactivateDisables sending and receiving data.
doEventsProcesses events from the internal message queue.
pauseDataPauses data reception.
processDataRe-enables data reception after a call to PauseData .
resetReset the component.
resolveRemoteHostResolves the hostname in RemoteHost to an IP address.
sendSends data to the remote host.
sendBytesSends data to the remote host.
sendTextSends data to the remote host.

Event List


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

DataInFired when data is received.
ErrorInformation about errors during data delivery.
ReadyToSendFired when the component is ready to send data.

Configuration Settings


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

CaptureIPPacketInfoUsed to capture the packet information.
DelayHostResolutionWhether the hostname is resolved when RemoteHost is set.
DestinationAddressUsed to get the destination address from the packet information.
DontFragmentUsed to set the Don't Fragment flag of outgoing packets.
LocalHostThe name of the local host through which connections are initiated or accepted.
LocalPortThe port in the local host where the component binds.
MaxPacketSizeThe maximum length of the packets that can be received.
QOSDSCPValueUsed to specify an arbitrary QOS/DSCP setting (optional).
QOSTrafficTypeUsed to specify QOS/DSCP settings (optional).
ShareLocalPortIf set to True, allows more than one instance of the component to be active on the same local port.
UseConnectionDetermines whether to use a connected socket.
UseIPv6Whether or not to use IPv6.
AbsoluteTimeoutDetermines whether timeouts are inactivity timeouts or absolute timeouts.
FirewallDataUsed to send extra data to the firewall.
InBufferSizeThe size in bytes of the incoming queue of the socket.
OutBufferSizeThe size in bytes of the outgoing queue of the socket.
BuildInfoInformation about the product's build.
GUIAvailableTells the component whether or not a message loop is available for processing events.
LicenseInfoInformation about the current license.
UseDaemonThreadsWhether threads created by the component are daemon threads.
UseInternalSecurityAPITells the component whether or not to use the system security libraries or an internal implementation.

AcceptData Property (MCast Component)

Enables or disables data reception (the DataIn event).

Syntax


public boolean isAcceptData();


public void setAcceptData(boolean acceptData);

Default Value

True

Remarks

This property enables or disables data reception (the DataIn event). Setting this property to False, temporarily disables data reception (and the DataIn event). Setting this property to True, re-enables data reception.

Note: It is recommended to use the PauseData or ProcessData method instead of setting this property.

This property is not available at design time.

Active Property (MCast Component)

Enables or disables sending and receiving data.

Syntax


public boolean isActive();


public void setActive(boolean active);

Default Value

False

Remarks

This property enables or disables sending and receiving data. Setting this property to True makes MCast create a communication endpoint (socket) which can be used for sending and receiving UDP datagrams. Setting this property to False destroys the socket and disables data communications.

Note: It is recommended to use the Activate or Deactivate method instead of setting this property.

This property is not available at design time.

LocalHost Property (MCast Component)

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

Syntax


public String getLocalHost();


public void setLocalHost(String localHost);

Default Value

""

Remarks

The LocalHost 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 multi-homed hosts (machines with more than one IP interface) setting LocalHost to the value of an interface will make the component initiate connections (or accept in the case of server components) only through that interface.

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 multi-homed 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.

LocalPort Property (MCast Component)

The UDP port in the local host where MCast binds.

Syntax


public int getLocalPort();


public void setLocalPort(int localPort);

Default Value

0

Remarks

This property must be set before MCast is activated (Active is set to True). It instructs the component to bind to a specific port (or communication endpoint) in the local machine.

Setting it to 0 (default) enables the system to choose a port at random. The chosen port will be shown by this property after the connection is established.

This property cannot be changed once the component is Active. Any attempt to set this property when the component is Active will generate an error.

This property is useful when trying to send data to services that require a trusted port in the client side.

Loopback Property (MCast Component)

Enables or disables loopback of data sent to the multicast group.

Syntax


public boolean isLoopback();


public void setLoopback(boolean loopback);

Default Value

True

Remarks

This property enables or disables loopback of data sent to the multicast group. Setting this property to False disables loopback of data sent through the component (normally loopback is enabled). This property is directly related to the IP_MULTICAST_LOOP socket option.

This property is not available at design time.

MulticastGroup Property (MCast Component)

Multicast group to join or leave.

Syntax


public String getMulticastGroup();


public void setMulticastGroup(String multicastGroup);

Default Value

""

Remarks

This property contains the multicast group to join or leave. Multicast groups are joined by assigning values to this property after the component is activated. More than one group may be joined at the same time. To define which interface to use, the ReceiveInterface property is used.

Determining whether a group is left or joined is done by setting the first letter of MulticastGroup is "-" or "+". The default operation is join.

To remove the component from a multicast group once it is joined, simply assign this groupname (address) to MulticastGroup prefixed by a minus sign "-".

Example (Joining/Leaving Groups)

MCastControl.Active = true MCastControl.MulticastGroup = "+231.31.31.31" MCastControl.MulticastGroup = "+232.32.32.32" MCastControl.MulticastGroup = "-232.32.32.32" MCastControl.MulticastGroup = "-231.31.31.31"

ReceiveInterface Property (MCast Component)

The interface with which to receive multicast packets. If empty, default is used.

Syntax


public String getReceiveInterface();


public void setReceiveInterface(String receiveInterface);

Default Value

""

Remarks

This property is useful when there is more than one network interface, and the one used for receiving multicast datagrams is not the default. If you wish to set an interface other than the system default, provide the IP address of the interface to be set.

This property is used together with the MulticastGroup property to join one or more multicast groups. The joining is done after the component is activated by assigning proper values to MulticastGroup.

This property is not available at design time.

RemoteHost Property (MCast Component)

The address of the remote host (multicast group).

Syntax


public String getRemoteHost();


public void setRemoteHost(String remoteHost);

Default Value

""

Remarks

This property contains the address of the remote host (multicast group). To send a multicast datagram, specify a RemoteHost value in the range of 224.0.0.0 to 239.255.255.255. These addresses are reserved as multicast addresses by IP.

RemotePort Property (MCast Component)

The UDP port in the remote host.

Syntax


public int getRemotePort();


public void setRemotePort(int remotePort);

Default Value

0

Remarks

This property contains the UDP port on the RemoteHost to send UDP datagrams to.

A valid port number (a value between 1 and 65535) is required.

SendInterface Property (MCast Component)

The interface from which multicast packets are sent. If empty, default is used.

Syntax


public String getSendInterface();


public void setSendInterface(String sendInterface);

Default Value

""

Remarks

This property is useful when there is more than one network interface, and the one used for sending multicast datagrams is not the default. If you wish to set an interface other than the system default, provide the IP address of the interface to be set.

This property is not available at design time.

TimeToLive Property (MCast Component)

The maximum number of subnets that a multicast datagram can traverse.

Syntax


public int getTimeToLive();


public void setTimeToLive(int timeToLive);

Default Value

7

Remarks

This property contains the maximum number of subnets that a multicast datagram can traverse. The default value for this property is 7. This is an arbitrary value. You need to specify a value suitable for your application.

Multicast datagrams with this property set to 0 are not transmitted on any subnetwork. Multicast datagrams with this property set to 1 are delivered only on the local network. Multicast datagrams with this property set to greater than 1 may be delivered to more than one subnetwork if there are one or more multicast routers attached to the first-hop subnetwork.

A multicast router does not forward multicast datagrams with destination addresses between 224.0.0.0 and 224.0.0.255, inclusive, regardless of their TimeToLive. This particular range of addresses is reserved for the use of routing protocols and other low-level topology discovery or maintenance protocols, such as gateway discovery and group membership reporting.

Activate Method (Mcast Component)

Enables sending and receiving data.

Syntax

public void activate();

Remarks

This method enables sending and receiving of data. When called the component will create a communication endpoint (socket) which can be used for sending and receiving UDP datagrams.

Config Method (Mcast Component)

Sets or retrieves a configuration setting.

Syntax

public String config(String configurationString);

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.

Deactivate Method (Mcast Component)

Disables sending and receiving data.

Syntax

public void deactivate();

Remarks

This method disables sending and receiving of data. When called the component will dstroy the existing socket and disable data communications.

DoEvents Method (Mcast Component)

Processes events from the internal message queue.

Syntax

public void 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.

PauseData Method (Mcast Component)

Pauses data reception.

Syntax

public void pauseData();

Remarks

This method pauses data reception when called. While data reception is paused the DataIn event will not fire. Call ProcessData to re-enable data reception.

ProcessData Method (Mcast Component)

Re-enables data reception after a call to PauseData .

Syntax

public void processData();

Remarks

This method re-enables data reception after a previous call to PauseData. When PauseData is called the DataIn event will not fire. To re-enable data reception and allow DataIn to fire call this method.

Note: This method is only used after previously calling PauseData. It does not need to be called to process incoming data by default.

Reset Method (Mcast Component)

Reset the component.

Syntax

public void reset();

Remarks

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

ResolveRemoteHost Method (Mcast Component)

Resolves the hostname in RemoteHost to an IP address.

Syntax

public void 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 necessary. If DelayHostResolution is true this method may be called to manually resolve RemoteHost if desired.

Send Method (Mcast Component)

Sends data to the remote host.

Syntax

public void send(byte[] text);

Remarks

This method sends data to the remote host. Calling this method is equivalent to setting the DataToSend property to Text.

SendBytes Method (Mcast Component)

Sends data to the remote host.

Syntax

public void sendBytes(byte[] data);

Remarks

This method sends data to the remote host. Calling this method is equivalent to call SendBytes/SendText method.

SendText Method (Mcast Component)

Sends data to the remote host.

Syntax

public void sendText(String text);

Remarks

This method sends data to the remote host. Calling this method is equivalent to call SendBytes/SendText method.

DataIn Event (Mcast Component)

Fired when data is received.

Syntax

public class DefaultMcastEventListener implements McastEventListener {
  ...
  public void dataIn(McastDataInEvent e) {}
  ...
}

public class McastDataInEvent {
  public byte[] datagram;

  public String sourceAddress;

  public int sourcePort;

}

Remarks

The DataIn event is fired every time a new datagram is received.

Datagram contains the packet as sent by the remote host.

SourceAddress contains the IP number (Internet address) of the remote host, and SourcePort contains the port from which the packet originated.

Note that events are not re-entrant. Performing time consuming operations within this event will prevent it from firing again in a timely manner and may impact overall performance.

Error Event (Mcast Component)

Information about errors during data delivery.

Syntax

public class DefaultMcastEventListener implements McastEventListener {
  ...
  public void error(McastErrorEvent e) {}
  ...
}

public class McastErrorEvent {
  public int errorCode;

  public String description;

}

Remarks

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

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

ReadyToSend Event (Mcast Component)

Fired when the component is ready to send data.

Syntax

public class DefaultMcastEventListener implements McastEventListener {
  ...
  public void readyToSend(McastReadyToSendEvent e) {}
  ...
}

public class McastReadyToSendEvent {
}

Remarks

The ReadyToSend event indicates that the underlying TCP/IP subsystem is ready to accept data after a failed DataToSend.

Configuration Settings (Mcast 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.

UDPPort Configuration Settings

CaptureIPPacketInfo:   Used to capture the packet information.

If this is set to true, the component will capture the IP packet information.

The default value for this setting is False.

Note: This setting is only available in Windows.

DelayHostResolution:   Whether the hostname is resolved when RemoteHost is set.

This setting specifies whether a hostname is resolved immediately when RemoteHost is set. If true the component will resolve the hostname and the IP address will be present in the RemoteHost property. If false, the hostname is not resolved until needed by the component when a method to connect or send data is called. If desired, ResolveRemoteHost may called to manually resolve the value in RemoteHost at any time.

The default value is false.

DestinationAddress:   Used to get the destination address from the packet information.

If CaptureIPPacketInfo is set to true, then this will be populated with the packet's destination address when a packet is received. This information will be accessible in the DataIn event.

Note: This setting is only available in Windows.

DontFragment:   Used to set the Don't Fragment flag of outgoing packets.

When set to True, packets sent by the component will have the Don't Fragment flag set. The default value is False.

LocalHost:   The name of the local host through which connections are initiated or accepted.

The LocalHost setting 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 multi-homed hosts (machines with more than one IP interface) setting LocalHost to the value of an interface will make the component initiate connections (or accept in the case of server components) only through that interface.

If the component is connected, the LocalHost setting 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 multi-homed hosts (machines with more than one IP interface).

LocalPort:   The port in the local host where the component binds.

This must be set before a connection is attempted. It instructs the component to bind to a specific port (or communication endpoint) in the local machine.

Setting this to 0 (default) enables the system to choose a port at random. The chosen port will be shown by LocalPort after the connection is established.

LocalPort cannot be changed once a connection is made. Any attempt to set this when a connection is active will generate an error.

This; setting is useful when trying to connect to services that require a trusted port in the client side. An example is the remote shell (rsh) service in UNIX systems.

MaxPacketSize:   The maximum length of the packets that can be received.

This setting specifies the maximum size of the datagrams that the component will accept without truncation.

QOSDSCPValue:   Used to specify an arbitrary QOS/DSCP setting (optional).

UseConnection must be True to use this setting. This option allows you to specify an arbitrary DSCP value between 0 and 63. The default is 0. When set to the default value the component will not set a DSCP value.

Note: This setting uses the qWAVE API is only available on Windows 7, Windows Server 2008 R2, and later.

QOSTrafficType:   Used to specify QOS/DSCP settings (optional).

UseConnection must be True to use this setting. You may specify either the text or integer values: BestEffort (0), Background (1), ExcellentEffort (2), AudioVideo (3), Voice (4), and Control (5).

Note: This setting uses the qWAVE API which is only available on Windows Vista and Windows Server 2008 or above.

Note: QOSTrafficType must be set before setting Active to true.

ShareLocalPort:   If set to True, allows more than one instance of the component to be active on the same local port.

This option must be set before the component is activated through the Active property or it will have no effect.

The default value for this setting is False.

UseConnection:   Determines whether to use a connected socket.

UseConnection specifies whether the component should use a connected socket or not. The connection is defined as an association in between the local address/port and the remote address/port. As such, this is not a connection in the traditional TCP sense. What it means is only that the component will send and receive data only to and from the specified destination.

The default value for this setting is False.

UseIPv6:   Whether or not to use IPv6.

By default, the component expects an IPv4 address for local and remote host properties, and will create an IPv4 socket. To use IPv6 instead, set this to True.

Socket Configuration Settings

AbsoluteTimeout:   Determines whether timeouts are inactivity timeouts or absolute timeouts.

If AbsoluteTimeout is set to True, any method which does not complete within Timeout seconds will be aborted. By default, AbsoluteTimeout is False, and the timeout is an inactivity timeout.

Note: This option is not valid for UDP ports.

FirewallData:   Used to send extra data to the firewall.

When the firewall is a tunneling proxy, use this property to send custom (additional) headers to the firewall (e.g. headers for custom authentication schemes).

InBufferSize:   The size in bytes of the incoming queue of the socket.

This is the size of an internal queue in the TCP/IP stack. You can increase or decrease its size depending on the amount of data that you will be receiving. Increasing the value of the InBufferSize setting can provide significant improvements in performance in some cases.

Some TCP/IP implementations do not support variable buffer sizes. If that is the case, when the component is activated the InBufferSize reverts to its defined size. The same happens if you attempt to make it too large or too small.

OutBufferSize:   The size in bytes of the outgoing queue of the socket.

This is the size of an internal queue in the TCP/IP stack. You can increase or decrease its size depending on the amount of data that you will be sending. Increasing the value of the OutBufferSize setting can provide significant improvements in performance in some cases.

Some TCP/IP implementations do not support variable buffer sizes. If that is the case, when the component is activated the OutBufferSize reverts to its defined size. The same happens if you attempt to make it too large or too small.

Base Configuration Settings

BuildInfo:   Information about the product's build.

When queried, this setting will return a string containing information about the product's build.

GUIAvailable:   Tells the component whether or not a message loop is available for processing events.

In a GUI-based application, long-running blocking operations may cause the application to stop responding to input until the operation returns. The component will attempt to discover whether or not the application has a message loop and, if one is discovered, it will process events in that message loop during any such blocking operation.

In some non-GUI applications, an invalid message loop may be discovered that will result in errant behavior. In these cases, setting GUIAvailable to false will ensure that the component does not attempt to process external events.

LicenseInfo:   Information about the current license.

When queried, this setting will return a string containing information about the license this instance of a component is using. It will return the following information:

  • Product: The product the license is for.
  • Product Key: The key the license was generated from.
  • License Source: Where the license was found (e.g., RuntimeLicense, License File).
  • License Type: The type of license installed (e.g., Royalty Free, Single Server).
UseDaemonThreads:   Whether threads created by the component are daemon threads.

If set to True (default), when the component creates a thread, the thread's Daemon property will be explicitly set to True. When set to False, the component will not set the Daemon property on the created thread. The default value is True.

UseInternalSecurityAPI:   Tells the component whether or not to use the system security libraries or an internal implementation.

By default the component will use the system security libraries to perform cryptographic functions. Setting this to True tells the component to use the internal implementation instead of using the system's security API.

Trappable Errors (Mcast Component)

MCast Errors

104   MCast is already Active.
106   You cannot change the LocalPort while the component is Active.
107   You cannot change the LocalHost at this time. A connection is in progress.
109   MCast must be Active for this operation.
112   Cannot change MaxPacketSize while the component is Active.

SSL Errors

270   Cannot load specified security library.
271   Cannot open certificate store.
272   Cannot find specified certificate.
273   Cannot acquire security credentials.
274   Cannot find certificate chain.
275   Cannot verify certificate chain.
276   Error during handshake.
280   Error verifying certificate.
281   Could not find client certificate.
282   Could not find server certificate.
283   Error encrypting data.
284   Error decrypting data.

TCP/IP Errors

10004   [10004] Interrupted system call.
10009   [10009] Bad file number.
10013   [10013] Access denied.
10014   [10014] Bad address.
10022   [10022] Invalid argument.
10024   [10024] Too many open files.
10035   [10035] Operation would block.
10036   [10036] Operation now in progress.
10037   [10037] Operation already in progress.
10038   [10038] Socket operation on non-socket.
10039   [10039] Destination address required.
10040   [10040] Message too long.
10041   [10041] Protocol wrong type for socket.
10042   [10042] Bad protocol option.
10043   [10043] Protocol not supported.
10044   [10044] Socket type not supported.
10045   [10045] Operation not supported on socket.
10046   [10046] Protocol family not supported.
10047   [10047] Address family not supported by protocol family.
10048   [10048] Address already in use.
10049   [10049] Can't assign requested address.
10050   [10050] Network is down.
10051   [10051] Network is unreachable.
10052   [10052] Net dropped connection or reset.
10053   [10053] Software caused connection abort.
10054   [10054] Connection reset by peer.
10055   [10055] No buffer space available.
10056   [10056] Socket is already connected.
10057   [10057] Socket is not connected.
10058   [10058] Can't send after socket shutdown.
10059   [10059] Too many references, can't splice.
10060   [10060] Connection timed out.
10061   [10061] Connection refused.
10062   [10062] Too many levels of symbolic links.
10063   [10063] File name too long.
10064   [10064] Host is down.
10065   [10065] No route to host.
10066   [10066] Directory not empty
10067   [10067] Too many processes.
10068   [10068] Too many users.
10069   [10069] Disc Quota Exceeded.
10070   [10070] Stale NFS file handle.
10071   [10071] Too many levels of remote in path.
10091   [10091] Network subsystem is unavailable.
10092   [10092] WINSOCK DLL Version out of range.
10093   [10093] Winsock not loaded yet.
11001   [11001] Host not found.
11002   [11002] Non-authoritative 'Host not found' (try again or check DNS setup).
11003   [11003] Non-recoverable errors: FORMERR, REFUSED, NOTIMP.
11004   [11004] Valid name, no data record (check DNS setup).

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IPWorks 2022 Android Edition - Version 22.0 [Build 8171]