MCast Module

Properties   Methods   Events   Config Settings   Errors  

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

Syntax

IPWorks.Mcast

Remarks

The MCast class is very similar to UDP, 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 class is activated). TimeToLive allows you 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 class 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 UDP, by calling the Send method with a Text parameter or with the DataToSend property. The destination is specified using the RemoteHost and RemotePort properties. Inbound data are received through the DataIn event.

Property List

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

Method List

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

Event List

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

Config Settings

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

AcceptData Property (MCast Module)

This property enables or disables data reception (the DataIn event).

Syntax

• Swift
• Objective-C

public var acceptData: Bool {
  get {...}
  set {...}
}

@property (nonatomic,readwrite,assign,getter=acceptData,setter=setAcceptData:) BOOL acceptData;

- (BOOL)acceptData;
- (void)setAcceptData :(BOOL)newAcceptData;

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, reenables data reception.

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

Active Property (MCast Module)

This property indicates whether the module is active.

Syntax

• Swift
• Objective-C

public var active: Bool {
  get {...}
  set {...}
}

@property (nonatomic,readwrite,assign,getter=active,setter=setActive:) BOOL active;

- (BOOL)active;
- (void)setActive :(BOOL)newActive;

Default Value

False

Remarks

This property indicates whether the class is currently active and can send or receive data.

When the class can be used for sending and receiving User Datagram Protocol (UDP) datagrams.

Note: Use the Activate or Deactivate method to control whether the class is active.

DataToSend Property (MCast Module)

This write-only property includes a string of data to be sent to the remote host.

Syntax

• Swift
• Objective-C

public var dataToSend: String {  set {...}
}

public var dataToSendB: Data {  set {...}
}

@property (nonatomic,readwrite,assign,getter=dataToSend,setter=setDataToSend:) NSString* dataToSend;

- (NSString*)dataToSend;
- (void)setDataToSend :(NSString*)newDataToSend;

@property (nonatomic,readwrite,assign,getter=dataToSendB,setter=setDataToSendB:) NSData* dataToSendB;

- (NSData*)dataToSendB;
- (void)setDataToSendB :(NSData*)newDataToSend;

Default Value

""

Remarks

This write-only property contains a string of data to be sent to the remote host. Assigning a string to this property makes the class send the string to the remote host. The Send method provides similar functionality.

The Transmission Control Protocol(TCP)/IP subsystem attempts to send the string assigned to this property as a complete message. If socket buffers are full, or the message cannot be delivered for any reason, an error is fired, and no portion of the message is sent. This is different from TCP in which portions of the messages can be sent. The class sends either a complete message or nothing at all.

If you are sending data to the remote host faster than it can process it, or faster than the network's bandwidth allows, the outgoing queue might fill up. When this happens, this property .

This property is write-only.

LocalHost Property (MCast Module)

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

Syntax

• Swift
• Objective-C

public var localHost: String {
  get {...}
  set {...}
}

@property (nonatomic,readwrite,assign,getter=localHost,setter=setLocalHost:) NSString* localHost;

- (NSString*)localHost;
- (void)setLocalHost :(NSString*)newLocalHost;

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 class initiate connections (or accept in the case of server classs) only through that interface.

If the class 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 Module)

This property includes the User Datagram Protocol (UDP) port in the local host where MCast binds.

Syntax

• Swift
• Objective-C

public var localPort: Int32 {
  get {...}
  set {...}
}

@property (nonatomic,readwrite,assign,getter=localPort,setter=setLocalPort:) int localPort;

- (int)localPort;
- (void)setLocalPort :(int)newLocalPort;

Default Value

0

Remarks

This property must be set before MCast is activated (Active is set to True). It instructs the class to bind to a specific port (or communication endpoint) on 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 class is Active. Any attempt to set this property when the class is Active will generate an error.

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

Loopback Property (MCast Module)

This property enables or disables loopback of data sent to the multicast group.

Syntax

• Swift
• Objective-C

public var loopback: Bool {
  get {...}
  set {...}
}

@property (nonatomic,readwrite,assign,getter=loopback,setter=setLoopback:) BOOL loopback;

- (BOOL)loopback;
- (void)setLoopback :(BOOL)newLoopback;

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 class (normally loopback is enabled). This property is directly related to the IP_MULTICAST_LOOP socket option.

MulticastGroup Property (MCast Module)

This property includes the multicast group to join or leave.

Syntax

• Swift
• Objective-C

public var multicastGroup: String {
  get {...}
  set {...}
}

@property (nonatomic,readwrite,assign,getter=multicastGroup,setter=setMulticastGroup:) NSString* multicastGroup;

- (NSString*)multicastGroup;
- (void)setMulticastGroup :(NSString*)newMulticastGroup;

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 class 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 to "-" or "+". The default operation is join.

To remove the class 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 Module)

This property includes the interface with which to receive multicast packets. If empty, the default is used.

Syntax

• Swift
• Objective-C

public var receiveInterface: String {
  get {...}
  set {...}
}

@property (nonatomic,readwrite,assign,getter=receiveInterface,setter=setReceiveInterface:) NSString* receiveInterface;

- (NSString*)receiveInterface;
- (void)setReceiveInterface :(NSString*)newReceiveInterface;

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 along with the MulticastGroup property to join one or more multicast groups. The joining is done after the class is activated by assigning proper values to MulticastGroup.

RemoteHost Property (MCast Module)

This property includes the address of the remote host (multicast group).

Syntax

• Swift
• Objective-C

public var remoteHost: String {
  get {...}
  set {...}
}

@property (nonatomic,readwrite,assign,getter=remoteHost,setter=setRemoteHost:) NSString* remoteHost;

- (NSString*)remoteHost;
- (void)setRemoteHost :(NSString*)newRemoteHost;

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 Module)

This property includes the User Datagram Protocol (UDP) port on the remote host.

Syntax

• Swift
• Objective-C

public var remotePort: Int32 {
  get {...}
  set {...}
}

@property (nonatomic,readwrite,assign,getter=remotePort,setter=setRemotePort:) int remotePort;

- (int)remotePort;
- (void)setRemotePort :(int)newRemotePort;

Default Value

0

Remarks

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

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

SendInterface Property (MCast Module)

This property includes the interface from which multicast packets are sent. If empty, the default is used.

Syntax

• Swift
• Objective-C

public var sendInterface: String {
  get {...}
  set {...}
}

@property (nonatomic,readwrite,assign,getter=sendInterface,setter=setSendInterface:) NSString* sendInterface;

- (NSString*)sendInterface;
- (void)setSendInterface :(NSString*)newSendInterface;

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.

TimeToLive Property (MCast Module)

This property includes the maximum number of subnets that a multicast datagram can traverse.

Syntax

• Swift
• Objective-C

public var timeToLive: Int32 {
  get {...}
  set {...}
}

@property (nonatomic,readwrite,assign,getter=timeToLive,setter=setTimeToLive:) int timeToLive;

- (int)timeToLive;
- (void)setTimeToLive :(int)newTimeToLive;

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 one or more multicast routers are 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 Module)

This method enables sending and receiving of data.

Syntax

• Swift
• Objective-C

public func activate() throws -> Void

- (void)activate;

Remarks

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

Config Method (MCast Module)

Sets or retrieves a configuration setting.

Syntax

• Swift
• Objective-C

public func config(configurationString: String) throws -> String

- (NSString*)config:(NSString*)configurationString;

Remarks

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

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

This method disables sending and receiving of data.

Syntax

• Swift
• Objective-C

public func deactivate() throws -> Void

- (void)deactivate;

Remarks

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

DoEvents Method (MCast Module)

Processes events from the internal message queue.

Syntax

• Swift
• Objective-C

public func doEvents() throws -> Void

- (void)doEvents;

Remarks

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

PauseData Method (MCast Module)

This method pauses data reception.

Syntax

• Swift
• Objective-C

public func pauseData() throws -> Void

- (void)pauseData;

Remarks

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

ProcessData Method (MCast Module)

This method reenables data reception after a call to PauseData .

Syntax

• Swift
• Objective-C

public func processData() throws -> Void

- (void)processData;

Remarks

This method reenables data reception after a previous call to PauseData. When PauseData is called, the DataIn event will not fire. To reenable data reception and allow DataIn to fire, call this method.

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

Reset Method (MCast Module)

This method resets the component.

Syntax

• Swift
• Objective-C

public func reset() throws -> Void

- (void)reset;

Remarks

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

ResolveRemoteHost Method (MCast Module)

Resolves the hostname in RemoteHost to an IP address.

Syntax

• Swift
• Objective-C

public func resolveRemoteHost() throws -> Void

- (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 class will resolve the hostname automatically when necessary. If DelayHostResolution is this method may be called to manually resolve RemoteHost if desired.

Send Method (MCast Module)

This method sends data to the remote host.

Syntax

• Swift
• Objective-C

public func send(text: Data) throws -> Void

- (void)send:(NSData*)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 Module)

This method sends data to the remote host.

Syntax

• Swift
• Objective-C

public func sendBytes(data: Data) throws -> Void

- (void)sendBytes:(NSData*)data;

Remarks

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

SendText Method (MCast Module)

This method sends data to the remote host.

Syntax

• Swift
• Objective-C

public func sendText(text: String) throws -> Void

- (void)sendText:(NSString*)text;

Remarks

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

DataIn Event (MCast Module)

Fired when data is received.

Syntax

• Swift
• Objective-C

func onDataIn(datagram: Data, sourceAddress: String, sourcePort: Int32)

- (void)onDataIn:(NSData*)datagram :(NSString*)sourceAddress :(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: Events are not re-entrant. Performing time-consuming operations within this event will prevent it from firing again in a timely manner and may affect overall performance.

Error Event (MCast Module)

Fired when information is available about errors during data delivery.

Syntax

• Swift
• Objective-C

func onError(errorCode: Int32, description: String)

- (void)onError:(int)errorCode :(NSString*)description;

Remarks

The Error event is fired in case of exceptional conditions during message processing. Normally the class .

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.

ReadyToSend Event (MCast Module)

Fired when the component is ready to send data.

Syntax

• Swift
• Objective-C

func onReadyToSend()

- (void)onReadyToSend;

Remarks

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

Config Settings (MCast Module)

UDP Config Settings

Socket Config Settings

Base Config Settings

Trappable Errors (MCast Module)

MCast Errors

SSL Errors

TCP/IP Errors