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tutorial for users "cannot work on my condition"

How to use this library on two VPSs.

purpose

I have designed this library that nobody worry about the there environment, no dependency on OS and written by pure-Python. However, some users submit report of dependence problem in unexpected condition. As far as I checked, it goes from network security policy to network adapter and etc. So, I wrote this tutorial that works in a universal environment by VPSs.

about VPS

Choose two complete independent VPS providers and choose the cheapest plan. I would recommend vulter and time4vps. Especially you can rent an hour on vulter by a few cents. If you already have a server, you can use it to save money, but you should be responsible because you need to set up a firewall, please be careful about mistakes.

rent VPS

You should check

  • Ubuntu (you can select other dist and windows but.. no guarantee)
  • Python3.6 or newer (default installed maybe but check)
  • PIP (default installed maybe but check)
  • protected by ufw (default deny)

prepare

  1. install pip3 install --user git+https://github.com/namuyan/srudp

  2. check ip by ip addr show

vps@store:~$ ip addr show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: venet0: <BROADCAST,POINTOPOINT,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN 
    link/void 
    inet 127.0.0.2/32 scope host venet0
    inet 11.22.33.44/32 brd 11.22.33.44 scope global venet0:0
    inet6 2a14:a311:aa80:63cf::1/128 scope global 
       valid_lft forever preferred_lft forever

find ipv4 11.22.33.44 and another side is 55.66.77.88.

setup one side

open repl.

[p2p@vps ~]$ python3
Python 3.7.2 (default, Mar  9 2019, 23:55:13) 
[GCC 4.8.5 20150623 (Red Hat 4.8.5-36)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from srudp import *
>>> sock = SecureReliableSocket()
>>> sock.connect(("11.22.33.44", 10020))  # don't type, wait!

setup another side

Python 3.6.2 (default, Jul 20 2017, 08:43:29) 
[GCC 5.4.1 20170519] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from srudp import *
>>> sock = SecureReliableSocket()
>>> sock.connect(("55.66.77.88", 10020))  # don't type, wait again!

establish connection

Let's type on two console by manual, don't need to be care about timing. This work to be executed in half a minutes, I think.

Nothing return? you may be success!

If raised error like below, hole-punch-message don't reach.

ConnectionError: timeout on hand shaking

send message and receive it

socket do auto ping-pong to maintain connection. You can see the work by logging on by debug level, but noisy.

Let's send message "hello world?"

>>> sock.sendall(b"hello world?")
>>>

And get the message by another side.

>>> sock.recv(1024)
b'hello world?'
>>>

advance stage 1, let's send big data

generate random 16Mb binary and send.

>>> import os
>>> from hashlib import sha256
>>> data = os.urandom(1024*1024*16)
>>> len(data)
16777216
>>> sha256(data).hexdigest()
'f6232284969ef76ad4baccd7d808eeb3a05686e0320a8661bddfd549c949a708'
>>> sock.sendall(data)

receive the data and check sha256.

>>> from hashlib import sha256
>>> sock.settimeout(30.0)
>>> data = b''
>>> while True:
        try:
...         data += sock.recv(8192)
...     except Exception as e:
...         print("timeout", e)
...         break
...
socket.timeout
>>> len(data)
16777216
>>> sha256(data).hexdigest()
'f6232284969ef76ad4baccd7d808eeb3a05686e0320a8661bddfd549c949a708'

You can send big data like TCP easily.

You may loss same packets when big data sending, you can know your internet stability by sock.loss.

>>> sock.loss / sock.receiver_seq * 100
0.151597273548493

I just transmitted from home PC at Japan to VPS hosted on Slovakia. This too long distance make me lost 0.15% of all packet.

advance stage 2, unreliable broadcast

You can send message like UDP, but you can't detect the data reached. It's good for P2P mesh network broadcasting, I think.

Just broadcast short message.

>>> sock.broadcast(b"why?")

And receive it.

>>> sock.recv(1024)
b'why?'

You can also hook the message like this. normal sock.sendall message go sock.recv, only broadcast message. You will have big latency when don't hook broadcast because normal data stream block broadcast to avoid confuse data.

>>> sock.broadcast_hook_fnc = lambda (p, s): print(p, ",", p.data)
Packet(BCT seq:0 retry:0 time:1591543763.87 data:4b) , b'why?'

close socket

close by sock.close() or ctrl+C. socket send close signal to other side.

Let's see socket status

>>> sock
<srudp.SecureReliableSocket [closed] fd=-1, family=AddressFamily.AF_INET, type=SocketKind.SOCK_DGRAM, proto=0>
>>>

questions

  1. You may have question "Which is server and client side?", the answer is "You don't need to worry about the features". SRUDP just send and receive UDP packet with only one side. It is true that the role is divided only in connection, but it is divided internally according to whether a punching message is "received" or "not received" by network communication delay.

  2. And you may have question "how to justify connection timing?", the answer is "You need to setup signaling server". I leave a implementation of this to the users, please.

recommend other challenge

  • connect your home and VPS or your friend
  • windows and Linux
  • Ipv6 connection
  • implement signaling system