twisted.protocols.amp.BinaryBoxProtocol(StatefulStringProtocol, Int16StringReceiver, _DescriptorExchanger) class documentation

Part of twisted.protocols.amp View Source (View In Hierarchy)

Known subclasses: twisted.protocols.amp.AMP

Implements interfaces: twisted.protocols.amp.IBoxSender

A protocol for receiving AmpBoxes - key/value pairs - via length-prefixed strings. A box is composed of:

  • any number of key-value pairs, described by:
    • a 2-byte network-endian packed key length (of which the first byte must be null, and the second must be non-null: i.e. the value of the length must be 1-255)
    • a key, comprised of that many bytes
    • a 2-byte network-endian unsigned value length (up to the maximum of 65535)
    • a value, comprised of that many bytes
  • 2 null bytes

In other words, an even number of strings prefixed with packed unsigned 16-bit integers, and then a 0-length string to indicate the end of the box.

This protocol also implements 2 extra private bits of functionality related to the byte boundaries between messages; it can start TLS between two given boxes or switch to an entirely different protocol. However, due to some tricky elements of the implementation, the public interface to this functionality is ProtocolSwitchCommand and StartTLS.

Instance Variable boxReceiver an IBoxReceiver provider, whose IBoxReceiver.ampBoxReceived method will be invoked for each AmpBox that is received.
Method __init__ Undocumented
Method sendBox Send a amp.Box to my peer.
Method makeConnection Notify boxReceiver that it is about to receive boxes from this protocol by invoking IBoxReceiver.startReceivingBoxes.
Method dataReceived Either parse incoming data as AmpBoxes or relay it to our nested protocol.
Method connectionLost The connection was lost; notify any nested protocol.
Method proto_init String received in the 'init' state.
Method proto_key String received in the 'key' state. If the key is empty, a complete box has been received.
Method proto_value String received in the 'value' state.
Method lengthLimitExceeded The key length limit was exceeded. Disconnect the transport and make sure a meaningful exception is reported.
Method unhandledError The buck stops here. This error was completely unhandled, time to terminate the connection.
Instance Variable _keyLengthLimitExceeded A flag which is only true when the connection is being closed because a key length prefix which was longer than allowed by the protocol was received.
Method _switchTo Switch this BinaryBoxProtocol's transport to a new protocol. You need to do this 'simultaneously' on both ends of a connection; the easiest way to do this is to use a subclass of ProtocolSwitchCommand.
Method _lockForSwitch No summary
Method _unlockFromSwitch Unlock this locked binary protocol so that further boxes may be sent again. This is used after an attempt to switch protocols has failed for some reason.
Method _prepareTLS Used by StartTLSCommand to put us into the state where we don't actually send things that get sent, instead we buffer them. see _sendBoxCommand.
Method _startTLS Used by TLSBox to initiate the SSL handshake.
Method _getPeerCertificate Undocumented
Method _defaultStartTLSResponder The default TLS responder doesn't specify any certificate or anything.

Inherited from StatefulStringProtocol:

Instance Variable state Current state of the protocol. Defaults to 'init'. (type: str)
Method stringReceived Choose a protocol phase function and call it.

Inherited from IntNStringReceiver (via Int16StringReceiver):

Instance Variable structFormat format used for struct packing/unpacking. Define it in subclass. (type: str)
Instance Variable prefixLength length of the prefix, in bytes. Define it in subclass, using struct.calcsize(structFormat) (type: int)
Method stringReceived Override this for notification when each complete string is received.
Method sendString Send a prefixed string to the other end of the connection.
Instance Variable _unprocessed bytes received, but not yet broken up into messages / sent to stringReceived. _compatibilityOffset must be updated when this value is updated so that the recvd attribute can be generated correctly. (type: bytes)
Instance Variable _compatibilityOffset the offset within _unprocessed to the next message to be parsed. (used to generate the recvd attribute) (type: int)

Inherited from Protocol (via Int16StringReceiver, IntNStringReceiver):

Method logPrefix Return a prefix matching the class name, to identify log messages related to this protocol instance.

Inherited from BaseProtocol (via Int16StringReceiver, IntNStringReceiver, Protocol):

Method connectionMade Called when a connection is made.

Inherited from _PauseableMixin (via Int16StringReceiver, IntNStringReceiver):

Method pauseProducing Undocumented
Method resumeProducing Undocumented
Method stopProducing Undocumented

Inherited from _DescriptorExchanger:

Method fileDescriptorReceived Collect received file descriptors to be claimed later by Descriptor.
Instance Variable _descriptors Temporary storage for all file descriptors received. Values in this dictionary are the file descriptors (as integers). Keys in this dictionary are ordinals giving the order in which each descriptor was received. The ordering information is used to allow Descriptor to determine which is the correct descriptor for any particular usage of that argument type. (type: dict)
Instance Variable _sendingDescriptorCounter A no-argument callable which returns the ordinals, starting from 0. This is used to construct values for _sendFileDescriptor.
Instance Variable _receivingDescriptorCounter A no-argument callable which returns the ordinals, starting from 0. This is used to construct values for fileDescriptorReceived.
Method _sendFileDescriptor Assign and return the next ordinal to the given descriptor after sending the descriptor over this protocol's transport.
_keyLengthLimitExceeded =
A flag which is only true when the connection is being closed because a key length prefix which was longer than allowed by the protocol was received.
boxReceiver =
an IBoxReceiver provider, whose IBoxReceiver.ampBoxReceived method will be invoked for each AmpBox that is received.
def __init__(self, boxReceiver): (source)
overrides twisted.protocols.amp._DescriptorExchanger.__init__
overridden in twisted.protocols.amp.AMP
Undocumented
def _switchTo(self, newProto, clientFactory=None): (source)

Switch this BinaryBoxProtocol's transport to a new protocol. You need to do this 'simultaneously' on both ends of a connection; the easiest way to do this is to use a subclass of ProtocolSwitchCommand.

ParametersnewProtothe new protocol instance to switch to.
clientFactorythe ClientFactory to send the twisted.internet.protocol.ClientFactory.clientConnectionLost notification to.
def sendBox(self, box): (source)
from twisted.protocols.amp.IBoxSender

Send a amp.Box to my peer.

Note: transport.write is never called outside of this method.

Parametersboxan AmpBox.
RaisesProtocolSwitchedif the protocol has previously been switched.
ConnectionLostif the connection has previously been lost.
def makeConnection(self, transport): (source)
from twisted.internet.interfaces.IProtocol
overrides twisted.internet.protocol.BaseProtocol.makeConnection
overridden in twisted.protocols.amp.AMP

Notify boxReceiver that it is about to receive boxes from this protocol by invoking IBoxReceiver.startReceivingBoxes.

def dataReceived(self, data): (source)
from twisted.internet.interfaces.IProtocol
overrides twisted.protocols.basic.IntNStringReceiver.dataReceived

Either parse incoming data as AmpBoxes or relay it to our nested protocol.

def connectionLost(self, reason): (source)
from twisted.internet.interfaces.IProtocol
overrides twisted.internet.protocol.Protocol.connectionLost
overridden in twisted.protocols.amp.AMP

The connection was lost; notify any nested protocol.

def proto_init(self, string): (source)

String received in the 'init' state.

def proto_key(self, string): (source)

String received in the 'key' state. If the key is empty, a complete box has been received.

def proto_value(self, string): (source)

String received in the 'value' state.

def lengthLimitExceeded(self, length): (source)
overrides twisted.protocols.basic.IntNStringReceiver.lengthLimitExceeded

The key length limit was exceeded. Disconnect the transport and make sure a meaningful exception is reported.

def _lockForSwitch(self): (source)

Lock this binary protocol so that no further boxes may be sent. This is used when sending a request to switch underlying protocols. You probably want to subclass ProtocolSwitchCommand rather than calling this directly.

def _unlockFromSwitch(self): (source)

Unlock this locked binary protocol so that further boxes may be sent again. This is used after an attempt to switch protocols has failed for some reason.

def _prepareTLS(self, certificate, verifyAuthorities): (source)

Used by StartTLSCommand to put us into the state where we don't actually send things that get sent, instead we buffer them. see _sendBoxCommand.

def _startTLS(self, certificate, verifyAuthorities): (source)

Used by TLSBox to initiate the SSL handshake.

Parameterscertificatea twisted.internet.ssl.PrivateCertificate for use locally.
verifyAuthoritiestwisted.internet.ssl.Certificate instances representing certificate authorities which will verify our peer.
def _getPeerCertificate(self): (source)
Undocumented
def unhandledError(self, failure): (source)
from twisted.protocols.amp.IBoxSender

The buck stops here. This error was completely unhandled, time to terminate the connection.

def _defaultStartTLSResponder(self): (source)

The default TLS responder doesn't specify any certificate or anything.

From a security perspective, it's little better than a plain-text connection - but it is still a *bit* better, so it's included for convenience.

You probably want to override this by providing your own StartTLS.responder.

API Documentation for Twisted, generated by pydoctor at 2018-10-15 19:29:43.