MCast Class

Properties   Methods   Events   Config Settings   Errors  

The MCast class 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

class 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 remote_host. To receive datagrams from one or more groups, assign the group addresses to multicast_group one by one (after the class is activated). time_to_live allows you to specify how many subnets a packet should be allowed to receive. receive_interface and send_interface 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. The destination is specified using the remote_host and remote_port properties. Inbound data are received through the on_data_in event.

Property List

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

accept_data Property

This property indicates whether data reception is currently enabled.

Syntax

def get_accept_data() -> bool: ...

accept_data = property(get_accept_data, None)

Default Value

TRUE

Remarks

This property indicates whether data reception is currently enabled. When False, data reception is disabled and the on_data_in event will not fire. Use the pause_data and process_data methods to pause and resume data reception.

This property is read-only.

active Property

This property indicates whether the class is active.

Syntax

def get_active() -> bool: ...

active = property(get_active, None)

Default Value

FALSE

Remarks

This property indicates whether the class is currently active and can send or receive data. Use the activate and deactivate methods to control whether the class is active.

This property is read-only.

local_host Property

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

Syntax

def get_local_host() -> str: ...
def set_local_host(value: str) -> None: ...

local_host = property(get_local_host, set_local_host)

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 class initiate connections (or accept in the case of server classs) 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 class is connected, the local_host 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: local_host is not persistent. You must always set it in code, and never in the property window.

local_port Property

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

Syntax

def get_local_port() -> int: ...
def set_local_port(value: int) -> None: ...

local_port = property(get_local_port, set_local_port)

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

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

Syntax

def get_loopback() -> bool: ...
def set_loopback(value: bool) -> None: ...

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

multicast_group Property

This property includes the multicast group to join or leave.

Syntax

def get_multicast_group() -> str: ...
def set_multicast_group(value: str) -> None: ...

multicast_group = property(get_multicast_group, set_multicast_group)

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 receive_interface property is used.

Determining whether a group is left or joined is done by setting the first letter of multicast_group 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 multicast_group 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"

receive_interface Property

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

Syntax

def get_receive_interface() -> str: ...
def set_receive_interface(value: str) -> None: ...

receive_interface = property(get_receive_interface, set_receive_interface)

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

remote_host Property

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

Syntax

def get_remote_host() -> str: ...
def set_remote_host(value: str) -> None: ...

remote_host = property(get_remote_host, set_remote_host)

Default Value

""

Remarks

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

remote_port Property

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

Syntax

def get_remote_port() -> int: ...
def set_remote_port(value: int) -> None: ...

remote_port = property(get_remote_port, set_remote_port)

Default Value

0

Remarks

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

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

send_interface Property

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

Syntax

def get_send_interface() -> str: ...
def set_send_interface(value: str) -> None: ...

send_interface = property(get_send_interface, set_send_interface)

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.

time_to_live Property

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

Syntax

def get_time_to_live() -> int: ...
def set_time_to_live(value: int) -> None: ...

time_to_live = property(get_time_to_live, set_time_to_live)

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 time_to_live. 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

This method enables sending and receiving of data.

Syntax

def activate() -> None: ...

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

Sets or retrieves a configuration setting.

Syntax

def config(configuration_string: str) -> str: ...

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

This method disables sending and receiving of data.

Syntax

def deactivate() -> None: ...

Remarks

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

do_events Method

This method processes events from the internal message queue.

Syntax

def do_events() -> None: ...

Remarks

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

pause_data Method

This method pauses data reception.

Syntax

def pause_data() -> None: ...

Remarks

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

process_data Method

This method reenables data reception after a call to PauseData .

Syntax

def process_data() -> None: ...

Remarks

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

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

reset Method

This method resets the class.

Syntax

def reset() -> None: ...

Remarks

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

resolve_remote_host Method

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

Syntax

def resolve_remote_host() -> None: ...

Remarks

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

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

send Method

This method sends data to the remote host.

Syntax

def send(text: bytes) -> None: ...

Remarks

This method sends data to the remote host.

send_bytes Method

This method sends data to the remote host.

Syntax

def send_bytes(data: bytes) -> None: ...

Remarks

This method sends data to the remote host. Calling this method is equivalent to calling the send_bytes/send_text method.

send_text Method

This method sends data to the remote host.

Syntax

def send_text(text: str) -> None: ...

Remarks

This method sends data to the remote host. Calling this method is equivalent to calling the send_bytes/send_text method.

on_data_in Event

This event is fired when data are received.

Syntax

class MCastDataInEventParams(object):
  @property
  def datagram() -> bytes: ...

  @property
  def source_address() -> str: ...

  @property
  def source_port() -> int: ...

# In class MCast:
@property
def on_data_in() -> Callable[[MCastDataInEventParams], None]: ...
@on_data_in.setter
def on_data_in(event_hook: Callable[[MCastDataInEventParams], None]) -> None: ...

Remarks

The on_data_in 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.

on_error Event

Fired when information is available about errors during data delivery.

Syntax

class MCastErrorEventParams(object):
  @property
  def error_code() -> int: ...

  @property
  def description() -> str: ...

# In class MCast:
@property
def on_error() -> Callable[[MCastErrorEventParams], None]: ...
@on_error.setter
def on_error(event_hook: Callable[[MCastErrorEventParams], None]) -> None: ...

Remarks

The on_error event is fired in case of exceptional conditions during message processing. Normally the class fails with an error.

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.

on_ready_to_send Event

This event is fired when the class is ready to send data.

Syntax

class MCastReadyToSendEventParams(object):
# In class MCast:
@property
def on_ready_to_send() -> Callable[[MCastReadyToSendEventParams], None]: ...
@on_ready_to_send.setter
def on_ready_to_send(event_hook: Callable[[MCastReadyToSendEventParams], None]) -> None: ...

Remarks

The on_ready_to_send event indicates that the underlying Transmission Control Protocol (TCP)/IP subsystem is ready to accept data after a failed send.

MCast Config Settings

The class 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 class, access to these internal properties is provided through the config method.

UDP Config Settings

Socket Config Settings

Base Config Settings

MCast Errors

MCast Errors

SSL Errors

TCP/IP Errors