slack.py

import socket
import ssl

def send_message():
    s = socket.socket()

    ai = socket.getaddrinfo("slack.com", 443)
    print("Address infos:", ai)
    addr = ai[0][-1]

    s.connect(addr)
    s = ssl.wrap_socket(s)

    send_data = "token=yourtoken&channel=%23yourchannel&text=Hello!! Meassage from Micropython&username=yourname"

    s.write(b"POST /api/chat.postMessage HTTP/1.1\r\n")
    s.write(b"Host: slack.com\r\n")
    s.write(b"Accept: */*\r\n")
    s.write(b"Content-Length: %d\r\n" % len(send_data))
    s.write(b"Content-Type: application/x-www-form-urlencoded\r\n")
    s.write(b"Connection: close\r\n")
    s.write(b"\r\n")
    s.write(send_data)

    print(s.read(4096))
    s.close()