Secure Reliable UDP

This repository provides Secure Reliable Data Stream that works like TCP.
My purpose is enable users create P2P connection between clients in closed NAT.

Features

Pure Python
Usage like normal socket object
Protocol similar to RUDP
UDP hole punching
high performance (4Mbps/s Up&Down when 10mb)
ipv4/ipv6
optional asyncio

Requirement

Python3.6+
requirements.txt

Installation

tutorial for users "cannot work on my condition"

pip3 install --user srudp

Tests

git clone https://github.com/namuyan/srudp
cd srudp
pip3 install --user -r requirements.txt
python3 -m mypy --config-file=mypy.ini srudp
python3 -m unittest discover

Demo

Prepare two independent PCs.

from srudp import SecureReliableSocket
from time import sleep, time
 
sock = SecureReliableSocket()
sock.connect(("<remote host 1>", 12345))
 
while not sock.is_closed:
    sock.sendall(b'hello ' + str(time()).encode())
    sleep(3)
print("closed", sock)

A side, send message hello once in a 3 sec.

from srudp import SecureReliableSocket
from time import time
 
sock = SecureReliableSocket()
sock.connect(("<remote host 2>", 12345))
 
while not sock.is_closed:
    data = sock.recv(1024)
    if not data:
        break
    print(time(), data)
print("closed", sock)

Another side, receive the message and show immediately.

asyncio usage

from srudp import SecureReliableSocket
import asyncio

# Get a reference to the current event loop
loop = asyncio.get_event_loop()

# create a socket
sock = SecureReliableSocket()

# connect() on another thread because block event loop
address = ("example.com", 3000)
await loop.run_in_executor(None, sock.connect, (address,))

# Register the open socket to wait for data
reader, writer = await asyncio.open_connection(sock=sock)

# read
data = await reader.read(1024)

# write
writer.write(b"hello")
writer.write(b"world")
await writer.drain()

# close
writer.close()

You can do just like a normal TCP socket. But if you don't intend, like HTTP protocol which requires a lot of connections, you don't have to use async method.

to avoid troubles

Do not think always success connection establish. Web-RTC detect UDP-hole-punching success, or use alternative way when failed, you need to implement it.
UDP (and some TCP) is often blocked on public network like airport free wifi and university local LAN etc. Addition to it, some router and network adapter sometimes block.
I designed this simple TCP like socket object. This don't have signaling function, haven't data specialized because I will use this as one of low-layer libraries for P2P.

Note: Why make this?

These days, PC is located in a local environment protected by NAT. It is difficult to transfer data between two outsides. In order to solve this problem, connection is realized by UDP hole punching without using UPnP.

UDP is a socket protocol with minimum functions for connecting applications. Therefore, there is no connection state, data may not be reachable, spoofing the source is easy. This is why, you cannot substitute it as TCP.

With this program, you can treat it just like TCP without worrying about the above problems. In other words, it has a connection state, guarantees data reachability, and is difficult to forge.

Author

@namuyan

Licence

MIT

ForestJ2/srudp