py2p 0.7.878

A python library for peer-to-peer networking

Basic Usage

To connect to a mesh network, you will use the MeshSocket object. You can instantiate this as follows:

>>> import py2p
>>> sock = py2p.MeshSocket('0.0.0.0', 4444)

Using '0.0.0.0' will automatically grab you LAN address. If you want to use an outward-facing internet connection, you will need to specify this address as follows:

>>> import py2p
>>> sock = py2p.MeshSocket('0.0.0.0', 4444, out_addr=('8.8.8.8', 8888))

In addition, you can enable SSL encryption if you have PyOpenSSL or cryptography installed. This works by specifying a custom protocol object, like so:

>>> import py2p
>>> sock = py2p.MeshSocket('0.0.0.0', 4444, prot=py2p.protocol('mesh', 'SSL'))

Eventually that will be the default, but while things are being tested it will default to plaintext. Specifying a different protocol object will ensure that you only can connect to people who share your object structure. So if someone has 'mesh2' instead of 'mesh', you will fail to connect.

Unfortunately, this failure is currently silent. Because this is asynchronous in nature, raising an Exception is not possible. Because of this, it’s good to perform the following check after connecting:

>>> import py2p, time
>>> sock = py2p.MeshSocket('0.0.0.0', 4444)
>>> sock.connect('192.168.1.14', 4567)
>>> time.sleep(1)
>>> assert sock.routing_table

To send a message, you should use the send method. Each argument you supply will correspond to a packet that your peer receives. In addition, there are two keyed arguments you can use. flag will specify how other nodes relay this. b'broadcast' will indicate that other nodes are supposed to relay it. b'whisper' will indicate that your peers are not supposed to relay it. There are other technically valid options, but they are not recommended. type will specify what actions other nodes are supposed to take on it. It defaults to b'broadcast', which indicates no change from the norm. There are other valid options, but they should normally be left alone, unless you’ve written a handler (see below) to act on this.

>>> sock.send('this is', 'a test')

Receiving is a bit simpler. When you call the recv method, you receive a Message object. This has a number of methods outlined here. Most notably, you can get the packets in a message with Message.packets, and reply directly with Message.reply().

>>> sock.send('Did you get this?')
>>> msg = sock.recv()
>>> print(msg)
Message(type=b'whisper', packets=[b'yes', b'I did'], sender=b'6VnYj9LjoVLTvU3uPhy4nxm6yv2wEvhaRtGHeV9wwFngWGGqKAzuZ8jK6gFuvq737V')
>>> print(msg.packets)
[b'whisper', b'yes', b'I did']
>>> for msg in sock.recv(10):
...     msg.reply("Replying to a list")

Advanced Usage

In addition to this, you can register a custom handler for incoming messages. This is appended to the end of the included ones. When writing your handler, you must keep in mind that you are only passed a Message object and a link to the receiving connection. Fortunately you can get access to everything you need from these objects. To see what methods each has, see the API docs. An example service would look like this:

>>> def relay_tx(msg, handler):
...     """Relays bitcoin transactions to various services"""
...     packets = msg.packets  # Gives a list of the non-metadata packets
...     server = msg.server    # Returns your MeshSocket object
...     if packets[0] == b'tx_relay':  # It's important that this flag is bytes
...         from pycoin import tx, services
...         relay = tx.Tx.from_bin(packets[1])
...         services.blockchain_info.send_tx(relay)
...         services.insight.InsightProvider().send_tx(relay)
...         return True        # This tells the daemon to stop calling handlers
...
>>> import py2p
>>> sock = py2p.MeshSocket('0.0.0.0', 4444)
>>> sock.register_handler(relay_tx)

If this does not take two arguments, register_handler will raise a ValueError. To help debug these services, you can specify a debug_level in the constructor. Using a value of 5, you can see when it enters into each handler, as well as every message which goes in or out.