# Python Distributed Hash Table
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**Documentation can be found at [kademlia.readthedocs.org](http://kademlia.readthedocs.org/).**

This library is an asynchronous Python implementation of the [Kademlia distributed hash table](http://en.wikipedia.org/wiki/Kademlia).  It uses the [asyncio library](https://docs.python.org/3/library/asyncio.html) in Python 3 to provide asynchronous communication.  The nodes communicate using [RPC over UDP](https://github.com/bmuller/rpcudp) to communiate, meaning that it is capable of working behind a [NAT](http://en.wikipedia.org/wiki/NAT).

This library aims to be as close to a reference implementation of the [Kademlia paper](http://pdos.csail.mit.edu/~petar/papers/maymounkov-kademlia-lncs.pdf) as possible.

## Installation

```
pip install kademlia
```

## Usage
*This assumes you have a working familiarity with [asyncio](https://docs.python.org/3/library/asyncio.html).*

Assuming you want to connect to an existing network:

```python
import asyncio
from kademlia.network import Server

# Create a node and start listening on port 5678
node = Server()
node.listen(5678)

# Bootstrap the node by connecting to other known nodes, in this case
# replace 123.123.123.123 with the IP of another node and optionally
# give as many ip/port combos as you can for other nodes.
loop = asyncio.get_event_loop()
loop.run_until_complete(node.bootstrap([("123.123.123.123", 5678)]))

# set a value for the key "my-key" on the network
loop.run_until_complete(node.set("my-key", "my awesome value"))

# get the value associated with "my-key" from the network
result = loop.run_until_complete(node.get("my-key"))
print(result)
```

## Initializing a Network
If you're starting a new network from scratch, just omit the `node.bootstrap` call in the example above.  Then, bootstrap other nodes by connecting to the first node you started.

See the examples folder for a first node example that other nodes can bootstrap connect to and some code that gets and sets a key/value.

## Logging
This library uses the standard [Python logging library](https://docs.python.org/3/library/logging.html).  To see debut output printed to STDOUT, for instance, use:

```python
import logging

log = logging.getLogger('kademlia')
log.setLevel(logging.DEBUG)
log.addHandler(logging.StreamHandler())
```

## Running Tests
To run tests:

```
pip install -r dev-requirements.txt
python -m unittest
```

## Fidelity to Original Paper
The current implementation should be an accurate implementation of all aspects of the paper save one - in Section 2.3 there is the requirement that the original publisher of a key/value republish it every 24 hours.  This library does not do this (though you can easily do this manually).