Reticulum/docs/markdown/reference.md

# API Reference

Communication over Reticulum networks is achieved by using a simple set of classes exposed by the RNS API.
This chapter lists and explains all classes exposed by the Reticulum Network Stack API, along with their method signatures and usage. It can be used as a reference while writing applications that utilise Reticulum, or it can be read in entirity to gain an understanding of the complete functionality of RNS from a developers perspective.

### `class RNS.Reticulum(configdir=None, loglevel=None, logdest=None, verbosity=None, require_shared_instance=False, shared_instance_type=None)`

This class is used to initialise access to Reticulum within a
program. You must create exactly one instance of this class before
carrying out any other RNS operations, such as creating destinations
or sending traffic. Every independently executed program must create
their own instance of the Reticulum class, but Reticulum will
automatically handle inter-program communication on the same system,
and expose all connected programs to external interfaces as well.

As soon as an instance of this class is created, Reticulum will start
opening and configuring any hardware devices specified in the supplied
configuration.

Currently the first running instance must be kept running while other
local instances are connected, as the first created instance will
act as a master instance that directly communicates with external
hardware such as modems, TNCs and radios. If a master instance is
asked to exit, it will not exit until all client processes have
terminated (unless killed forcibly).

If you are running Reticulum on a system with several different
programs that use RNS starting and terminating at different times,
it will be advantageous to run a master RNS instance as a daemon for
other programs to use on demand.

#### `MTU = 500`

The MTU that Reticulum adheres to, and will expect other peers to
adhere to. By default, the MTU is 500 bytes. In custom RNS network
implementations, it is possible to change this value, but doing so will
completely break compatibility with all other RNS networks. An identical
MTU is a prerequisite for peers to communicate in the same network.

Unless you really know what you are doing, the MTU should be left at
the default value.

#### `LINK_MTU_DISCOVERY = True`

Whether automatic link MTU discovery is enabled by default. Link MTU
discovery significantly increases throughput over fast links.

#### `ANNOUNCE_CAP = 2`

The maximum percentage of interface bandwidth that, at any given time,
may be used to propagate announces. If an announce was scheduled for
broadcasting on an interface, but doing so would exceed the allowed
bandwidth allocation, the announce will be queued for transmission
when there is bandwidth available.

Reticulum will always prioritise propagating announces with fewer
hops, ensuring that distant, large networks with many peers on fast
links don’t overwhelm the capacity of smaller networks on slower
mediums. If an announce remains queued for an extended amount of time,
it will eventually be dropped.

This value will be applied by default to all created interfaces,
but it can be configured individually on a per-interface basis. In
general, the global default setting should not be changed, and any
alterations should be made on a per-interface basis instead.

#### `MINIMUM_BITRATE = 5`

Minimum bitrate required across a medium for Reticulum to be able
to successfully establish links. Currently 5 bits per second.

#### `static get_instance()`

Return the currently running Reticulum instance

#### `static should_use_implicit_proof()`

Returns whether proofs sent are explicit or implicit.

* **Returns:**
  True if the current running configuration specifies to use implicit proofs. False if not.

#### `static transport_enabled()`

Returns whether Transport is enabled for the running
instance.

When Transport is enabled, Reticulum will
route traffic for other peers, respond to path requests
and pass announces over the network.

* **Returns:**
  True if Transport is enabled, False if not.

#### `static link_mtu_discovery()`

Returns whether link MTU discovery is enabled for the running
instance.

When link MTU discovery is enabled, Reticulum will
automatically upgrade link MTUs to the highest supported
value, increasing transfer speed and efficiency.

* **Returns:**
  True if link MTU discovery is enabled, False if not.

#### `static remote_management_enabled()`

Returns whether remote management is enabled for the
running instance.

When remote management is enabled, authenticated peers
can remotely query and manage this instance.

* **Returns:**
  True if remote management is enabled, False if not.

#### `static required_discovery_value()`

Returns the required stamp value for a discovered interface
to be considered valid and remembered.

* **Returns:**
  The required stamp value as an integer.

#### `static publish_blackhole_enabled()`

Returns whether blackhole list publishing is enabled for the
running instance.

* **Returns:**
  True if blackhole list publishing is enabled, False if not.

#### `static blackhole_sources()`

Returns the list of transport identity hashes from which
blackhole lists are sourced.

* **Returns:**
  A list of identity hashes.

#### `static discovered_interfaces()`

Returns a list of interfaces discovered over the network.

* **Returns:**
  A list of discovered interfaces.

#### `static interface_discovery_sources()`

Returns the list of network identity hashes from which
interfaces are discovered.

* **Returns:**
  A list of identity hashes.

### `class RNS.Identity(create_keys=True)`

This class is used to manage identities in Reticulum. It provides methods
for encryption, decryption, signatures and verification, and is the basis
for all encrypted communication over Reticulum networks.

* **Parameters:**
  **create_keys** – Specifies whether new encryption and signing keys should be generated.

#### `CURVE = 'Curve25519'`

The curve used for Elliptic Curve DH key exchanges

#### `KEYSIZE = 512`

X.25519 key size in bits. A complete key is the concatenation of a 256 bit encryption key, and a 256 bit signing key.

#### `RATCHETSIZE = 256`

X.25519 ratchet key size in bits.

#### `RATCHET_EXPIRY = 2592000`

The expiry time for received ratchets in seconds, defaults to 30 days. Reticulum will always use the most recently
announced ratchet, and remember it for up to `RATCHET_EXPIRY` since receiving it, after which it will be discarded.
If a newer ratchet is announced in the meantime, it will be replace the already known ratchet.

#### `TRUNCATED_HASHLENGTH = 128`

Constant specifying the truncated hash length (in bits) used by Reticulum
for addressable hashes and other purposes. Non-configurable.

#### `static recall(target_hash, from_identity_hash=False, _no_use=False)`

Recall identity for a destination or identity hash. By default, this function
will return the identity associated with a given *destination* hash. As an
example, if you know the `lxmf.delivery` destination hash of an endpoint,
this function will return the associated underlying identity. You can also
search for an identity from a known *identity hash*, by setting the
`from_identity_hash` argument.

* **Parameters:**
  * **target_hash** – Destination or identity hash as *bytes*.
  * **from_identity_hash** – Whether to search based on identity hash instead of destination hash as *bool*.
* **Returns:**
  An [RNS.Identity](#api-identity) instance that can be used to create an outgoing [RNS.Destination](#api-destination), or *None* if the destination is unknown.

#### `static recall_app_data(destination_hash, _no_use=False)`

Recall last heard app_data for a destination hash.

* **Parameters:**
  **destination_hash** – Destination hash as *bytes*.
* **Returns:**
  *Bytes* containing app_data, or *None* if the destination is unknown.

#### `static full_hash(data)`

Get a SHA-256 hash of passed data.

* **Parameters:**
  **data** – Data to be hashed as *bytes*.
* **Returns:**
  SHA-256 hash as *bytes*.

#### `static truncated_hash(data)`

Get a truncated SHA-256 hash of passed data.

* **Parameters:**
  **data** – Data to be hashed as *bytes*.
* **Returns:**
  Truncated SHA-256 hash as *bytes*.

#### `static get_random_hash()`

Get a random SHA-256 hash.

* **Parameters:**
  **data** – Data to be hashed as *bytes*.
* **Returns:**
  Truncated SHA-256 hash of random data as *bytes*.

#### `static current_ratchet_id(destination_hash)`

Get the ID of the currently used ratchet key for a given destination hash

* **Parameters:**
  **destination_hash** – A destination hash as *bytes*.
* **Returns:**
  A ratchet ID as *bytes* or *None*.

#### `static from_bytes(prv_bytes)`

Create a new [RNS.Identity](#api-identity) instance from *bytes* of private key.
Can be used to load previously created and saved identities into Reticulum.

* **Parameters:**
  **prv_bytes** – The *bytes* of private a saved private key. **HAZARD!** Never use this to generate a new key by feeding random data in prv_bytes.
* **Returns:**
  A [RNS.Identity](#api-identity) instance, or *None* if the *bytes* data was invalid.

#### `static from_file(path)`

Create a new [RNS.Identity](#api-identity) instance from a file.
Can be used to load previously created and saved identities into Reticulum.

* **Parameters:**
  **path** – The full path to the saved [RNS.Identity](#api-identity) data
* **Returns:**
  A [RNS.Identity](#api-identity) instance, or *None* if the loaded data was invalid.

#### `to_file(path)`

Saves the identity to a file. This will write the private key to disk,
and anyone with access to this file will be able to decrypt all
communication for the identity. Be very careful with this method.

* **Parameters:**
  **path** – The full path specifying where to save the identity.
* **Returns:**
  True if the file was saved, otherwise False.

#### `get_private_key()`

* **Returns:**
  The private key as *bytes*

#### `get_public_key()`

* **Returns:**
  The public key as *bytes*

#### `load_private_key(prv_bytes)`

Load a private key into the instance.

* **Parameters:**
  **prv_bytes** – The private key as *bytes*.
* **Returns:**
  True if the key was loaded, otherwise False.

#### `load_public_key(pub_bytes)`

Load a public key into the instance.

* **Parameters:**
  **pub_bytes** – The public key as *bytes*.
* **Returns:**
  True if the key was loaded, otherwise False.

#### `encrypt(plaintext, ratchet=None)`

Encrypts information for the identity.

* **Parameters:**
  **plaintext** – The plaintext to be encrypted as *bytes*.
* **Returns:**
  Ciphertext token as *bytes*.
* **Raises:**
  *KeyError* if the instance does not hold a public key.

#### `decrypt(ciphertext_token, ratchets=None, enforce_ratchets=False, ratchet_id_receiver=None)`

Decrypts information for the identity.

* **Parameters:**
  **ciphertext** – The ciphertext to be decrypted as *bytes*.
* **Returns:**
  Plaintext as *bytes*, or *None* if decryption fails.
* **Raises:**
  *KeyError* if the instance does not hold a private key.

#### `sign(message)`

Signs information by the identity.

* **Parameters:**
  **message** – The message to be signed as *bytes*.
* **Returns:**
  Signature as *bytes*.
* **Raises:**
  *KeyError* if the instance does not hold a private key.

#### `validate(signature, message)`

Validates the signature of a signed message.

* **Parameters:**
  * **signature** – The signature to be validated as *bytes*.
  * **message** – The message to be validated as *bytes*.
* **Returns:**
  True if the signature is valid, otherwise False.
* **Raises:**
  *KeyError* if the instance does not hold a public key.

### `class RNS.Destination(identity, direction, type, app_name, \aspects)`

A class used to describe endpoints in a Reticulum Network. Destination
instances are used both to create outgoing and incoming endpoints. The
destination type will decide if encryption, and what type, is used in
communication with the endpoint. A destination can also announce its
presence on the network, which will distribute necessary keys for
encrypted communication with it.

* **Parameters:**
  * **identity** – An instance of [RNS.Identity](#api-identity). Can hold only public keys for an outgoing destination, or holding private keys for an ingoing.
  * **direction** – `RNS.Destination.IN` or `RNS.Destination.OUT`.
  * **type** – `RNS.Destination.SINGLE`, `RNS.Destination.GROUP` or `RNS.Destination.PLAIN`.
  * **app_name** – A string specifying the app name.
  * **\*aspects** – Any non-zero number of string arguments.

#### `RATCHET_COUNT = 512`

The default number of generated ratchet keys a destination will retain, if it has ratchets enabled.

#### `RATCHET_INTERVAL = 1800`

The minimum interval between rotating ratchet keys, in seconds.

#### `static expand_name(identity, app_name, \aspects)`

* **Returns:**
  A string containing the full human-readable name of the destination, for an app_name and a number of aspects.

#### `static app_and_aspects_from_name(full_name)`

* **Returns:**
  A tuple containing the app name and a list of aspects, for a full-name string.

#### `static hash_from_name_and_identity(full_name, identity)`

* **Returns:**
  A destination name in adressable hash form, for a full name string and Identity instance.

#### `static hash(identity, app_name, \aspects)`

* **Returns:**
  A destination name in adressable hash form, for an app_name and a number of aspects.

#### `announce(app_data=None, path_response=False, attached_interface=None, tag=None, send=True)`

Creates an announce packet for this destination and broadcasts it on all
relevant interfaces. Application specific data can be added to the announce.

* **Parameters:**
  * **app_data** – *bytes* containing the app_data.
  * **path_response** – Internal flag used by [RNS.Transport](#api-transport). Ignore.

#### `accepts_links(accepts=None)`

Set or query whether the destination accepts incoming link requests.

* **Parameters:**
  **accepts** – If `True` or `False`, this method sets whether the destination accepts incoming link requests. If not provided or `None`, the method returns whether the destination currently accepts link requests.
* **Returns:**
  `True` or `False` depending on whether the destination accepts incoming link requests, if the *accepts* parameter is not provided or `None`.

#### `set_link_established_callback(callback)`

Registers a function to be called when a link has been established to
this destination.

* **Parameters:**
  **callback** – A function or method with the signature *callback(link)* to be called when a new link is established with this destination.

#### `set_packet_callback(callback)`

Registers a function to be called when a packet has been received by
this destination.

* **Parameters:**
  **callback** – A function or method with the signature *callback(data, packet)* to be called when this destination receives a packet.

#### `set_proof_requested_callback(callback)`

Registers a function to be called when a proof has been requested for
a packet sent to this destination. Allows control over when and if
proofs should be returned for received packets.

* **Parameters:**
  **callback** – A function or method to with the signature *callback(packet)* be called when a packet that requests a proof is received. The callback must return one of True or False. If the callback returns True, a proof will be sent. If it returns False, a proof will not be sent.

#### `set_proof_strategy(proof_strategy)`

Sets the destinations proof strategy.

* **Parameters:**
  **proof_strategy** – One of `RNS.Destination.PROVE_NONE`, `RNS.Destination.PROVE_ALL` or `RNS.Destination.PROVE_APP`. If `RNS.Destination.PROVE_APP` is set, the proof_requested_callback will be called to determine whether a proof should be sent or not.

#### `register_request_handler(path, response_generator=None, allow=ALLOW_NONE, allowed_list=None, auto_compress=True)`

Registers a request handler.

* **Parameters:**
  * **path** – The path for the request handler to be registered.
  * **response_generator** – A function or method with the signature *response_generator(path, data, request_id, link_id, remote_identity, requested_at)* to be called. Whatever this funcion returns will be sent as a response to the requester. If the function returns `None`, no response will be sent.
  * **allow** – One of `RNS.Destination.ALLOW_NONE`, `RNS.Destination.ALLOW_ALL` or `RNS.Destination.ALLOW_LIST`. If `RNS.Destination.ALLOW_LIST` is set, the request handler will only respond to requests for identified peers in the supplied list.
  * **allowed_list** – A list of *bytes-like* [RNS.Identity](#api-identity) hashes.
  * **auto_compress** – If `True` or `False`, determines whether automatic compression of responses should be carried out. If set to an integer value, responses will only be auto-compressed if under this size in bytes. If omitted, the default compression settings will be followed.
* **Raises:**
  `ValueError` if any of the supplied arguments are invalid.

#### `deregister_request_handler(path)`

Deregisters a request handler.

* **Parameters:**
  **path** – The path for the request handler to be deregistered.
* **Returns:**
  True if the handler was deregistered, otherwise False.

#### `enable_ratchets(ratchets_path)`

Enables ratchets on the destination. When ratchets are enabled, Reticulum will automatically rotate
the keys used to encrypt packets to this destination, and include the latest ratchet key in announces.

Enabling ratchets on a destination will provide forward secrecy for packets sent to that destination,
even when sent outside a `Link`. The normal Reticulum `Link` establishment procedure already performs
its own ephemeral key exchange for each link establishment, which means that ratchets are not necessary
to provide forward secrecy for links.

Enabling ratchets will have a small impact on announce size, adding 32 bytes to every sent announce.

* **Parameters:**
  **ratchets_path** – The path to a file to store ratchet data in.
* **Returns:**
  True if the operation succeeded, otherwise False.

#### `enforce_ratchets()`

When ratchet enforcement is enabled, this destination will never accept packets that use its
base Identity key for encryption, but only accept packets encrypted with one of the retained
ratchet keys.

#### `set_retained_ratchets(retained_ratchets)`

Sets the number of previously generated ratchet keys this destination will retain,
and try to use when decrypting incoming packets. Defaults to `Destination.RATCHET_COUNT`.

* **Parameters:**
  **retained_ratchets** – The number of generated ratchets to retain.
* **Returns:**
  True if the operation succeeded, False if not.

#### `set_ratchet_interval(interval)`

Sets the minimum interval in seconds between ratchet key rotation.
Defaults to `Destination.RATCHET_INTERVAL`.

* **Parameters:**
  **interval** – The minimum interval in seconds.
* **Returns:**
  True if the operation succeeded, False if not.

#### `create_keys()`

For a `RNS.Destination.GROUP` type destination, creates a new symmetric key.

* **Raises:**
  `TypeError` if called on an incompatible type of destination.

#### `get_private_key()`

For a `RNS.Destination.GROUP` type destination, returns the symmetric private key.

* **Raises:**
  `TypeError` if called on an incompatible type of destination.

#### `load_private_key(key)`

For a `RNS.Destination.GROUP` type destination, loads a symmetric private key.

* **Parameters:**
  **key** – A *bytes-like* containing the symmetric key.
* **Raises:**
  `TypeError` if called on an incompatible type of destination.

#### `encrypt(plaintext)`

Encrypts information for `RNS.Destination.SINGLE` or `RNS.Destination.GROUP` type destination.

* **Parameters:**
  **plaintext** – A *bytes-like* containing the plaintext to be encrypted.
* **Raises:**
  `ValueError` if destination does not hold a necessary key for encryption.

#### `decrypt(ciphertext)`

Decrypts information for `RNS.Destination.SINGLE` or `RNS.Destination.GROUP` type destination.

* **Parameters:**
  **ciphertext** – *Bytes* containing the ciphertext to be decrypted.
* **Raises:**
  `ValueError` if destination does not hold a necessary key for decryption.

#### `sign(message)`

Signs information for `RNS.Destination.SINGLE` type destination.

* **Parameters:**
  **message** – *Bytes* containing the message to be signed.
* **Returns:**
  A *bytes-like* containing the message signature, or *None* if the destination could not sign the message.

#### `set_default_app_data(app_data=None)`

Sets the default app_data for the destination. If set, the default
app_data will be included in every announce sent by the destination,
unless other app_data is specified in the *announce* method.

* **Parameters:**
  **app_data** – A *bytes-like* containing the default app_data, or a *callable* returning a *bytes-like* containing the app_data.

#### `clear_default_app_data()`

Clears default app_data previously set for the destination.

### `class RNS.Packet(destination, data, create_receipt=True)`

The Packet class is used to create packet instances that can be sent
over a Reticulum network. Packets will automatically be encrypted if
they are addressed to a `RNS.Destination.SINGLE` destination,
`RNS.Destination.GROUP` destination or a [RNS.Link](#api-link).

For `RNS.Destination.GROUP` destinations, Reticulum will use the
pre-shared key configured for the destination. All packets to group
destinations are encrypted with the same AES-256 key.

For `RNS.Destination.SINGLE` destinations, Reticulum will use a newly
derived ephemeral AES-256 key for every packet.

For [RNS.Link](#api-link) destinations, Reticulum will use per-link
ephemeral keys, and offers **Forward Secrecy**.

* **Parameters:**
  * **destination** – A [RNS.Destination](#api-destination) instance to which the packet will be sent.
  * **data** – The data payload to be included in the packet as *bytes*.
  * **create_receipt** – Specifies whether a [RNS.PacketReceipt](#api-packetreceipt) should be created when instantiating the packet.

#### `ENCRYPTED_MDU = 383`

The maximum size of the payload data in a single encrypted packet

#### `PLAIN_MDU = 464`

The maximum size of the payload data in a single unencrypted packet

#### `send()`

Sends the packet.

* **Returns:**
  A [RNS.PacketReceipt](#api-packetreceipt) instance if *create_receipt* was set to *True* when the packet was instantiated, if not returns *None*. If the packet could not be sent *False* is returned.

#### `resend()`

Re-sends the packet.

* **Returns:**
  A [RNS.PacketReceipt](#api-packetreceipt) instance if *create_receipt* was set to *True* when the packet was instantiated, if not returns *None*. If the packet could not be sent *False* is returned.

#### `get_rssi()`

* **Returns:**
  The physical layer *Received Signal Strength Indication* if available, otherwise `None`.

#### `get_snr()`

* **Returns:**
  The physical layer *Signal-to-Noise Ratio* if available, otherwise `None`.

#### `get_q()`

* **Returns:**
  The physical layer *Link Quality* if available, otherwise `None`.

### `class RNS.PacketReceipt`

The PacketReceipt class is used to receive notifications about
[RNS.Packet](#api-packet) instances sent over the network. Instances
of this class are never created manually, but always returned from
the *send()* method of a [RNS.Packet](#api-packet) instance.

#### `get_status()`

* **Returns:**
  The status of the associated [RNS.Packet](#api-packet) instance. Can be one of `RNS.PacketReceipt.SENT`, `RNS.PacketReceipt.DELIVERED`, `RNS.PacketReceipt.FAILED` or `RNS.PacketReceipt.CULLED`.

#### `get_rtt()`

* **Returns:**
  The round-trip-time in seconds

#### `set_timeout(timeout)`

Sets a timeout in seconds

* **Parameters:**
  **timeout** – The timeout in seconds.

#### `set_delivery_callback(callback)`

Sets a function that gets called if a successfull delivery has been proven.

* **Parameters:**
  **callback** – A *callable* with the signature *callback(packet_receipt)*

#### `set_timeout_callback(callback)`

Sets a function that gets called if the delivery times out.

* **Parameters:**
  **callback** – A *callable* with the signature *callback(packet_receipt)*

### `class RNS.Link(destination, established_callback=None, closed_callback=None)`

This class is used to establish and manage links to other peers. When a
link instance is created, Reticulum will attempt to establish verified
and encrypted connectivity with the specified destination.

* **Parameters:**
  * **destination** – A [RNS.Destination](#api-destination) instance which to establish a link to.
  * **established_callback** – An optional function or method with the signature *callback(link)* to be called when the link has been established.
  * **closed_callback** – An optional function or method with the signature *callback(link)* to be called when the link is closed.

#### `CURVE = 'Curve25519'`

The curve used for Elliptic Curve DH key exchanges

#### `ESTABLISHMENT_TIMEOUT_PER_HOP = 6`

Timeout for link establishment in seconds per hop to destination.

#### `KEEPALIVE_TIMEOUT_FACTOR = 4`

RTT timeout factor used in link timeout calculation.

#### `STALE_GRACE = 5`

Grace period in seconds used in link timeout calculation.

#### `KEEPALIVE = 360`

Default interval for sending keep-alive packets on established links in seconds.

#### `STALE_TIME = 720`

If no traffic or keep-alive packets are received within this period, the
link will be marked as stale, and a final keep-alive packet will be sent.
If after this no traffic or keep-alive packets are received within `RTT` \*
`KEEPALIVE_TIMEOUT_FACTOR` + `STALE_GRACE`, the link is considered timed out,
and will be torn down.

#### `identify(identity)`

Identifies the initiator of the link to the remote peer. This can only happen
once the link has been established, and is carried out over the encrypted link.
The identity is only revealed to the remote peer, and initiator anonymity is
thus preserved. This method can be used for authentication.

* **Parameters:**
  **identity** – An RNS.Identity instance to identify as.

#### `request(path, data=None, response_callback=None, failed_callback=None, progress_callback=None, timeout=None)`

Sends a request to the remote peer.

* **Parameters:**
  * **path** – The request path.
  * **response_callback** – An optional function or method with the signature *response_callback(request_receipt)* to be called when a response is received. See the [Request Example](examples.md#example-request) for more info.
  * **failed_callback** – An optional function or method with the signature *failed_callback(request_receipt)* to be called when a request fails. See the [Request Example](examples.md#example-request) for more info.
  * **progress_callback** – An optional function or method with the signature *progress_callback(request_receipt)* to be called when progress is made receiving the response. Progress can be accessed as a float between 0.0 and 1.0 by the *request_receipt.progress* property.
  * **timeout** – An optional timeout in seconds for the request. If *None* is supplied it will be calculated based on link RTT.
* **Returns:**
  A [RNS.RequestReceipt](#api-requestreceipt) instance if the request was sent, or *False* if it was not.

#### `track_phy_stats(track)`

You can enable physical layer statistics on a per-link basis. If this is enabled,
and the link is running over an interface that supports reporting physical layer
statistics, you will be able to retrieve stats such as *RSSI*, *SNR* and physical
*Link Quality* for the link.

* **Parameters:**
  **track** – Whether or not to keep track of physical layer statistics. Value must be `True` or `False`.

#### `get_rssi()`

* **Returns:**
  The physical layer *Received Signal Strength Indication* if available, otherwise `None`. Physical layer statistics must be enabled on the link for this method to return a value.

#### `get_snr()`

* **Returns:**
  The physical layer *Signal-to-Noise Ratio* if available, otherwise `None`. Physical layer statistics must be enabled on the link for this method to return a value.

#### `get_q()`

* **Returns:**
  The physical layer *Link Quality* if available, otherwise `None`. Physical layer statistics must be enabled on the link for this method to return a value.

#### `get_establishment_rate()`

* **Returns:**
  The data transfer rate at which the link establishment procedure ocurred, in bits per second.

#### `get_mtu()`

* **Returns:**
  The MTU of an established link.

#### `get_mdu()`

* **Returns:**
  The packet MDU of an established link.

#### `get_expected_rate()`

* **Returns:**
  The packet expected in-flight data rate of an established link.

#### `get_mode()`

* **Returns:**
  The mode of an established link.

#### `get_age()`

* **Returns:**
  The time in seconds since this link was established.

#### `no_inbound_for()`

* **Returns:**
  The time in seconds since last inbound packet on the link. This includes keepalive packets.

#### `no_outbound_for()`

* **Returns:**
  The time in seconds since last outbound packet on the link. This includes keepalive packets.

#### `no_data_for()`

* **Returns:**
  The time in seconds since payload data traversed the link. This excludes keepalive packets.

#### `inactive_for()`

* **Returns:**
  The time in seconds since activity on the link. This includes keepalive packets.

#### `get_remote_identity()`

* **Returns:**
  The identity of the remote peer, if it is known. Calling this method will not query the remote initiator to reveal its identity. Returns `None` if the link initiator has not already independently called the `identify(identity)` method.

#### `teardown()`

Closes the link and purges encryption keys. New keys will
be used if a new link to the same destination is established.

#### `get_channel()`

Get the `Channel` for this link.

* **Returns:**
  `Channel` object

#### `set_link_closed_callback(callback)`

Registers a function to be called when a link has been
torn down.

* **Parameters:**
  **callback** – A function or method with the signature *callback(link)* to be called.

#### `set_packet_callback(callback)`

Registers a function to be called when a packet has been
received over this link.

* **Parameters:**
  **callback** – A function or method with the signature *callback(message, packet)* to be called.

#### `set_resource_callback(callback)`

Registers a function to be called when a resource has been
advertised over this link. If the function returns *True*
the resource will be accepted. If it returns *False* it will
be ignored.

* **Parameters:**
  **callback** – A function or method with the signature *callback(resource)* to be called. Please note that only the basic information of the resource is available at this time, such as *get_transfer_size()*, *get_data_size()*, *get_parts()* and *is_compressed()*.

#### `set_resource_started_callback(callback)`

Registers a function to be called when a resource has begun
transferring over this link.

* **Parameters:**
  **callback** – A function or method with the signature *callback(resource)* to be called.

#### `set_resource_concluded_callback(callback)`

Registers a function to be called when a resource has concluded
transferring over this link.

* **Parameters:**
  **callback** – A function or method with the signature *callback(resource)* to be called.

#### `set_remote_identified_callback(callback)`

Registers a function to be called when an initiating peer has
identified over this link.

* **Parameters:**
  **callback** – A function or method with the signature *callback(link, identity)* to be called.

#### `set_resource_strategy(resource_strategy)`

Sets the resource strategy for the link.

* **Parameters:**
  **resource_strategy** – One of `RNS.Link.ACCEPT_NONE`, `RNS.Link.ACCEPT_ALL` or `RNS.Link.ACCEPT_APP`. If `RNS.Link.ACCEPT_APP` is set, the resource_callback will be called to determine whether the resource should be accepted or not.
* **Raises:**
  *TypeError* if the resource strategy is unsupported.

### `class RNS.RequestReceipt`

An instance of this class is returned by the `request` method of `RNS.Link`
instances. It should never be instantiated manually. It provides methods to
check status, response time and response data when the request concludes.

#### `get_request_id()`

* **Returns:**
  The request ID as *bytes*.

#### `get_status()`

* **Returns:**
  The current status of the request, one of `RNS.RequestReceipt.FAILED`, `RNS.RequestReceipt.SENT`, `RNS.RequestReceipt.DELIVERED`, `RNS.RequestReceipt.READY`.

#### `get_progress()`

* **Returns:**
  The progress of a response being received as a *float* between 0.0 and 1.0.

#### `get_response()`

* **Returns:**
  The response as *bytes* if it is ready, otherwise *None*.

#### `get_response_time()`

* **Returns:**
  The response time of the request in seconds.

#### `concluded()`

* **Returns:**
  True if the associated request has concluded (successfully or with a failure), otherwise False.

### `class RNS.Resource(data, link, advertise=True, auto_compress=True, callback=None, progress_callback=None, timeout=None)`

The Resource class allows transferring arbitrary amounts
of data over a link. It will automatically handle sequencing,
compression, coordination and checksumming.

* **Parameters:**
  * **data** – The data to be transferred. Can be *bytes* or an open *file handle*. See the [Filetransfer Example](examples.md#example-filetransfer) for details.
  * **link** – The [RNS.Link](#api-link) instance on which to transfer the data.
  * **advertise** – Optional. Whether to automatically advertise the resource. Can be *True* or *False*.
  * **auto_compress** – Optional. Whether to auto-compress the resource. Can be *True* or *False*.
  * **callback** – An optional *callable* with the signature *callback(resource)*. Will be called when the resource transfer concludes.
  * **progress_callback** – An optional *callable* with the signature *callback(resource)*. Will be called whenever the resource transfer progress is updated.

#### `advertise()`

Advertise the resource. If the other end of the link accepts
the resource advertisement it will begin transferring.

#### `cancel()`

Cancels transferring the resource.

#### `get_progress()`

* **Returns:**
  The current progress of the resource transfer as a *float* between 0.0 and 1.0.

#### `get_transfer_size()`

* **Returns:**
  The number of bytes needed to transfer the resource.

#### `get_data_size()`

* **Returns:**
  The total data size of the resource.

#### `get_parts()`

* **Returns:**
  The number of parts the resource will be transferred in.

#### `get_segments()`

* **Returns:**
  The number of segments the resource is divided into.

#### `get_hash()`

* **Returns:**
  The hash of the resource.

#### `is_compressed()`

* **Returns:**
  Whether the resource is compressed.

### `class RNS.Channel.Channel`

Provides reliable delivery of messages over
a link.

`Channel` differs from `Request` and
`Resource` in some important ways:

> **Continuous**
> : Messages can be sent or received as long as
>   the `Link` is open.

> **Bi-directional**
> : Messages can be sent in either direction on
>   the `Link`; neither end is the client or
>   server.

> **Size-constrained**
> : Messages must be encoded into a single packet.

`Channel` is similar to `Packet`, except that it
provides reliable delivery (automatic retries) as well
as a structure for exchanging several types of
messages over the `Link`.

`Channel` is not instantiated directly, but rather
obtained from a `Link` with `get_channel()`.

#### `register_message_type(message_class: Type[[MessageBase](#RNS.MessageBase)])`

Register a message class for reception over a `Channel`.

Message classes must extend `MessageBase`.

* **Parameters:**
  **message_class** – Class to register

#### `add_message_handler(callback: MessageCallbackType)`

Add a handler for incoming messages. A handler
has the following signature:

`(message: MessageBase) -> bool`

Handlers are processed in the order they are
added. If any handler returns True, processing
of the message stops; handlers after the
returning handler will not be called.

* **Parameters:**
  **callback** – Function to call

#### `remove_message_handler(callback: MessageCallbackType)`

Remove a handler added with `add_message_handler`.

* **Parameters:**
  **callback** – handler to remove

#### `is_ready_to_send() → bool`

Check if `Channel` is ready to send.

* **Returns:**
  True if ready

#### `send(message: [MessageBase](#RNS.MessageBase)) → Envelope`

Send a message. If a message send is attempted and
`Channel` is not ready, an exception is thrown.

* **Parameters:**
  **message** – an instance of a `MessageBase` subclass

#### `property mdu`

Maximum Data Unit: the number of bytes available
for a message to consume in a single send. This
value is adjusted from the `Link` MDU to accommodate
message header information.

* **Returns:**
  number of bytes available

### `class RNS.MessageBase`

Base type for any messages sent or received on a Channel.
Subclasses must define the two abstract methods as well as
the `MSGTYPE` class variable.

#### `MSGTYPE = None`

Defines a unique identifier for a message class.

* Must be unique within all classes registered with a `Channel`
* Must be less than `0xf000`. Values greater than or equal to `0xf000` are reserved.

#### `abstractmethod pack() → bytes`

Create and return the binary representation of the message

* **Returns:**
  binary representation of message

#### `abstractmethod unpack(raw: bytes)`

Populate message from binary representation

* **Parameters:**
  **raw** – binary representation

### `class RNS.Buffer`

Static functions for creating buffered streams that send
and receive over a `Channel`.

These functions use `BufferedReader`, `BufferedWriter`,
and `BufferedRWPair` to add buffering to
`RawChannelReader` and `RawChannelWriter`.

#### `static create_reader(stream_id: int, channel: [Channel](#RNS.Channel.Channel), ready_callback: Callable[[int], None] | None = None) → BufferedReader`

Create a buffered reader that reads binary data sent
over a `Channel`, with an optional callback when
new data is available.

Callback signature: `(ready_bytes: int) -> None`

For more information on the reader-specific functions
of this object, see the Python documentation for
`BufferedReader`

* **Parameters:**
  * **stream_id** – the local stream id to receive from
  * **channel** – the channel to receive on
  * **ready_callback** – function to call when new data is available
* **Returns:**
  a BufferedReader object

#### `static create_writer(stream_id: int, channel: [Channel](#RNS.Channel.Channel)) → BufferedWriter`

Create a buffered writer that writes binary data over
a `Channel`.

For more information on the writer-specific functions
of this object, see the Python documentation for
`BufferedWriter`

* **Parameters:**
  * **stream_id** – the remote stream id to send to
  * **channel** – the channel to send on
* **Returns:**
  a BufferedWriter object

#### `static create_bidirectional_buffer(receive_stream_id: int, send_stream_id: int, channel: [Channel](#RNS.Channel.Channel), ready_callback: Callable[[int], None] | None = None) → BufferedRWPair`

Create a buffered reader/writer pair that reads and
writes binary data over a `Channel`, with an
optional callback when new data is available.

Callback signature: `(ready_bytes: int) -> None`

For more information on the reader-specific functions
of this object, see the Python documentation for
`BufferedRWPair`

* **Parameters:**
  * **receive_stream_id** – the local stream id to receive at
  * **send_stream_id** – the remote stream id to send to
  * **channel** – the channel to send and receive on
  * **ready_callback** – function to call when new data is available
* **Returns:**
  a BufferedRWPair object

### `class RNS.RawChannelReader(stream_id: int, channel: [Channel](#RNS.Channel.Channel))`

An implementation of RawIOBase that receives
binary stream data sent over a `Channel`.

> This class generally need not be instantiated directly.
> Use [`RNS.Buffer.create_reader()`](#RNS.Buffer.create_reader),
> [`RNS.Buffer.create_writer()`](#RNS.Buffer.create_writer), and
> [`RNS.Buffer.create_bidirectional_buffer()`](#RNS.Buffer.create_bidirectional_buffer) functions
> to create buffered streams with optional callbacks.

> For additional information on the API of this
> object, see the Python documentation for
> `RawIOBase`.

#### `__init__(stream_id: int, channel: [Channel](#RNS.Channel.Channel))`

Create a raw channel reader.

* **Parameters:**
  * **stream_id** – local stream id to receive at
  * **channel** – `Channel` object to receive from

#### `add_ready_callback(cb: Callable[[int], None])`

Add a function to be called when new data is available.
The function should have the signature `(ready_bytes: int) -> None`

* **Parameters:**
  **cb** – function to call

#### `remove_ready_callback(cb: Callable[[int], None])`

Remove a function added with [`RNS.RawChannelReader.add_ready_callback()`](#RNS.RawChannelReader.add_ready_callback)

* **Parameters:**
  **cb** – function to remove

### `class RNS.RawChannelWriter(stream_id: int, channel: [Channel](#RNS.Channel.Channel))`

An implementation of RawIOBase that receives
binary stream data sent over a channel.

> This class generally need not be instantiated directly.
> Use [`RNS.Buffer.create_reader()`](#RNS.Buffer.create_reader),
> [`RNS.Buffer.create_writer()`](#RNS.Buffer.create_writer), and
> [`RNS.Buffer.create_bidirectional_buffer()`](#RNS.Buffer.create_bidirectional_buffer) functions
> to create buffered streams with optional callbacks.

> For additional information on the API of this
> object, see the Python documentation for
> `RawIOBase`.

#### `__init__(stream_id: int, channel: [Channel](#RNS.Channel.Channel))`

Create a raw channel writer.

* **Parameters:**
  * **stream_id** – remote stream id to sent do
  * **channel** – `Channel` object to send on

### `class RNS.Transport`

Through static methods of this class you can interact with the
Transport system of Reticulum.

#### `PATHFINDER_M = 128`

Maximum amount of hops that Reticulum will transport a packet.

#### `static register_announce_handler(handler)`

Registers an announce handler.

* **Parameters:**
  **handler** – Must be an object with an *aspect_filter* attribute and a *received_announce(destination_hash, announced_identity, app_data)*
  or *received_announce(destination_hash, announced_identity, app_data, announce_packet_hash)* or
  *received_announce(destination_hash, announced_identity, app_data, announce_packet_hash, is_path_response)* callable. Can
  optionally have a *receive_path_responses* attribute set to `True`, to also receive all path responses, in addition to live
  announces. See the [Announce Example](examples.md#example-announce) for more info.

#### `static deregister_announce_handler(handler)`

Deregisters an announce handler.

* **Parameters:**
  **handler** – The announce handler to be deregistered.

#### `static has_path(destination_hash)`

* **Parameters:**
  **destination_hash** – A destination hash as *bytes*.
* **Returns:**
  *True* if a path to the destination is known, otherwise *False*.

#### `static hops_to(destination_hash)`

* **Parameters:**
  **destination_hash** – A destination hash as *bytes*.
* **Returns:**
  The number of hops to the specified destination, or `RNS.Transport.PATHFINDER_M` if the number of hops is unknown.

#### `static next_hop(destination_hash)`

* **Parameters:**
  **destination_hash** – A destination hash as *bytes*.
* **Returns:**
  The destination hash as *bytes* for the next hop to the specified destination, or *None* if the next hop is unknown.

#### `static next_hop_interface(destination_hash)`

* **Parameters:**
  **destination_hash** – A destination hash as *bytes*.
* **Returns:**
  The interface for the next hop to the specified destination, or *None* if the interface is unknown.

#### `static await_path(destination_hash, timeout=None, on_interface=None)`

Requests a path to the destination from the network and
blocks until the path is available, or the timeout is reached.

* **Parameters:**
  * **destination_hash** – A destination hash as *bytes*.
  * **timeout** – An optional timeout in seconds.
  * **on_interface** – If specified, the path request will only be sent on this interface. In normal use, Reticulum handles this automatically, and this parameter should not be used.
* **Returns:**
  *True* if a path to the destination is found, otherwise *False*.

#### `static request_path(destination_hash, on_interface=None, tag=None, recursive=False)`

Requests a path to the destination from the network. If
another reachable peer on the network knows a path, it
will announce it.

* **Parameters:**
  * **destination_hash** – A destination hash as *bytes*.
  * **on_interface** – If specified, the path request will only be sent on this interface. In normal use, Reticulum handles this automatically, and this parameter should not be used.