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Sans-IO pattern, language server protocol implementation

Project description

Language Server Protocol implementation in sans-io pattern. Which is highly inspired by Sans-IO pattern. And some relatived projects: - hyper-h2 - h11

So it can be integreted with trio, asyncio, or some other frameworks easily.

Required python version

Python >= 3.6


  1. Pure python implementation
  2. Don’t relatived to other site-packages
  3. Can (should) easily integreted with high level framework like trio, asyncio

How to install it

There are two ways to install lsp

  • Install via pip (recommended)
pip install lsp
  • Install via
python install

Basic Usage example

Client side

import socket
from lsp import Connection, NEED_DATA, DataReceived, MessageEnd

sock = socket.socket()

sock.connect(("localhost", 10001))
conn = Connection("client")

answer = input("Send request?(y/n)")
while answer == "y":
    # use connection send_json method to convert json object to bytes
    request_data = conn.send_json({"method": "didOpen"})
    # then we can send data to server

    while True:
        # and then we can get next_event of connection, it can indicate
        # that what should we do.
        event = conn.next_event()
        # we need to receive data from server
        if event is NEED_DATA:
                data = sock.recv(1024)
            except ConnectionResetError:
                print('The server connection is closed, So I will leave:)')
                print("return from sock.recv")
        # we have receive data from server
        elif isinstance(event, DataReceived):
            print("Receive event, content:")
        elif isinstance(event, MessageEnd):
            print("Server sending data complete.")

    # then we can call get_received_data() to extract out what we get
    header, response_body = conn.get_received_data()
    print("Response header from server:")
    print("Response body from server:")
    answer = input("Send request?(y/n)")

Server side

import socket
from lsp import Connection, NEED_DATA, RequestReceived, DataReceived, MessageEnd

sock = socket.socket()
sock.bind(("", 10001))
client_sock, addr = sock.accept()
print(f"get connection from {client_sock}")

conn = Connection("server")
    while True:
        while True:
            # call next event to indicate what server socket should do.
            event = conn.next_event()

            # no data coming yet, so the return value is NEED_DATA
            if event is NEED_DATA:
                data = client_sock.recv(1024)
                if data == b"":
                    print("Client connection is closed, I will exit.")
            # Request header is coming :)
            elif isinstance(event, RequestReceived):
                print("Receive request header")
            # Request data is coming :)
            elif isinstance(event, DataReceived):
                print("Receive request data")
            # client has send data completely.
            elif isinstance(event, MessageEnd):
                print("Data receive complete:)")

        # so we can call con.get_received_data to fetch what client send.
        received_data = conn.get_received_data()
        print(f"Receiving data: {received_data}")

        # send response back to client.
        print(f"Sending response to client")
        data = conn.send_json({"Content": "I am received:)"})
        print(f"For now, go to next circle")

        # then we need to call go_next_circle, to get another request from client.

For more usage example, please check out files in examples/servers folder.

Main API in lsp

  1. Want to send json data? You can try conn.send_json.
  2. Want to know what we should do next? You can try conn.next_event.
  3. After receive data, please don’t forget to call conn.receive(data). Which will save data into inner buffer, and it can drive conn.next_event method returns other events.
  4. When Receive MessageEnd event, we can just call conn.get_received_data to fetch for incoming data.

Main events we will get from next_event


Client side will get the following values from next_events:

  1. NEED_DATA - which indicate that we need to receive data from server.
  2. ResponseReceived - Client have receive response header.
  3. DataReceived - Client have receive resposne body.
  4. MessageEnd - Receive data from server complete.


Server side will get the following values from next_events:

  1. NEED_DATA - which indicate that we need to receive data from client.
  2. RequestReceived - Client have send request header, and we receive it.
  3. DataReceived - Server have receive response body from client.
  4. MessageEnd - Client sending request complete.

Project details

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