use paramiko create a simple ssh server in win7

I use the paramiko to create a simple ssh server in win7, just wanna execute command in win7 when a client connected.
#!/usr/bin/env python
#coding : utf-8

import base64
from binascii import hexlify
import os
import socket
import sys
import threading
import traceback

import paramiko
from paramiko.py3compat import b, u, decodebytes

#setup logging
paramiko.util.log_to_file("demo_server.log")

host_key = paramiko.RSAKey(filename="",password='')
#host_key = paramiko.DSSKey(filename='test_dss.key')

#print("Read key: " + u(hexlify(host_key.get_fingerprint())))

class Server(paramiko.ServerInterface):
with open('test.pub','r') as f :
good_pub_key=str(f.readlines())

def __init__(self):
    self.event = threading.Event()

def check_channel_request(self, kind, chanid):
    if kind == "session":
        return paramiko.OPEN_SUCCEEDED
    return paramiko.OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED

def check_auth_password(self, username, password):
    if (username == "******") and (password == "******"):
        return paramiko.AUTH_SUCCESSFUL
    return paramiko.AUTH_FAILED

def check_auth_publickey(self, username, key):
    print("Auth attempt with key: " + u(hexlify(key.get_fingerprint())))
    if (username == "root") and (key == self.good_pub_key):
        return paramiko.AUTH_SUCCESSFUL
    return paramiko.AUTH_FAILED

def check_auth_gssapi_with_mic(
    self, username, gss_authenticated=paramiko.AUTH_FAILED, cc_file=None
):
    if gss_authenticated == paramiko.AUTH_SUCCESSFUL:
        return paramiko.AUTH_SUCCESSFUL
    return paramiko.AUTH_FAILED

def check_auth_gssapi_keyex(
    self, username, gss_authenticated=paramiko.AUTH_FAILED, cc_file=None
):
    if gss_authenticated == paramiko.AUTH_SUCCESSFUL:
        return paramiko.AUTH_SUCCESSFUL
    return paramiko.AUTH_FAILED

def enable_auth_gssapi(self):
    return True

def get_allowed_auths(self, username):
    return "gssapi-keyex,gssapi-with-mic,password,publickey"

def check_channel_shell_request(self, channel):
    self.event.set()
    return True

def check_channel_pty_request(
    self, channel, term, width, height, pixelwidth, pixelheight, modes
):
    return True

def windows_shell(chan):
import threading
import subprocess

sys.stdout.write(
    "terminal emulation. Press F6 or ^Z to send EOF.\r\n\r\n"
)
def writeall(sock):
    #sock.send(('ssh > $:').encode('utf-8'))
    while True:
        sock.send(('ssh > $:').encode('utf-8'))
        data = sock.recv(1024).decode()
        if not data and data == 'exit':
            break
        try:
            output=subprocess.check_output(data,shell=True,stderr=subprocess.STDOUT)
            sock.send(output)
        except Exception as e:
            sock.send('execute error!\r\n')
    sock.close()
writer = threading.Thread(target=writeall, args=(chan,))
writer.start()
writer.join()
#writeall(sock)

DoGSSAPIKeyExchange = False

#now connect
try:
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sock.bind(("", 22))
except Exception as e:
print("*** Bind failed: " + str(e))
traceback.print_exc()
sys.exit(1)

try:
sock.listen(100)
print("Listening for connection ...")
client, addr = sock.accept()
except Exception as e:
print("*** Listen/accept failed: " + str(e))
traceback.print_exc()
sys.exit(1)

print("Got a connection!")

try:
t = paramiko.Transport(client, gss_kex=DoGSSAPIKeyExchange)
t.set_gss_host(socket.getfqdn(""))
try:
t.load_server_moduli()
except:
print("(Failed to load moduli -- gex will be unsupported.)")
raise
t.add_server_key(host_key)
server = Server()
try:
t.start_server(server=server)
except paramiko.SSHException:
print("*** SSH negotiation failed.")
sys.exit(1)

#wait for auth
chan = t.accept(200)
if chan is None:
    print("*** No channel.")
    sys.exit(1)
print("Authenticated!")

windows_shell(chan)
t.close()
sys.exit(0)

except Exception as e:
print("*** Caught exception: " + str(e.class) + ": " + str(e))
traceback.print_exc()
try:
t.close()
except:
pass
sys.exit(1)

I use a subprocess.check_out to get a shell in win7, but when i use linux to connect the ssh server, the command is ssh *******@win7'ip , auth successful and connected. but when i enter the command in the linux, I just can enter a character . This is the first question
another question is i cannot use the putty in win7 to connect the ssh server in win7 . I donot know why

Start by running the supplied server and reading the windows_shell loop, especially its subprocess.check_output call, then trace the Transport.start_server and channel-handling entry points. Compare the Linux SSH and PuTTY connection paths. Done means identifying the cause of the single-character input behavior and the failed PuTTY connection, with both cases reproducibly addressed.