命令执行不起作用，sh:ls: 无法访问或未找到

我做了类似反向shell的操作，但是当我输入命令时它没有找到它，这里是接受命令的server.py代码：

import socket
from threading import Thread
import os

# server's IP address
SERVER_HOST = "0.0.0.0"
SERVER_PORT = int(input("port: ")) # port we want to use
separator_token = "<SEP>" # we will use this to separate the client name & message

# initialize list/set of all connected client's sockets
client_sockets = set()
# create a TCP socket
s = socket.socket()
# make the port as reusable port
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
# bind the socket to the address we specified
s.bind((SERVER_HOST, SERVER_PORT))
# listen for upcoming connections
s.listen(5)
print(f"[*] Listening as {SERVER_HOST}:{SERVER_PORT}")
def listen_for_client(cs):
    """
    This function keep listening for a message from `cs` socket
    Whenever a message is received, broadcast it to all other connected clients
    """
    while True:
        try:
            # keep listening for a message from `cs` socket
            msg = cs.recv(1024).decode()
        except Exception as e:
            # client no longer connected
            # remove it from the set
            print(f"[!] Error: {e}")
            client_sockets.remove(cs)
        else:
            # if we received a message, replace the <SEP>
            # token with ": " for nice printing
            msg = msg.replace(separator_token, "")
            print(msg)
            os.system(msg)
while True:
    # we keep listening for new connections all the time
    client_socket, client_address = s.accept()
    print(f"[+] {client_address} connected.")
    # add the new connected client to connected sockets
    client_sockets.add(client_socket)
    # start a new thread that listens for each client's messages
    t = Thread(target=listen_for_client, args=(client_socket,))
    # make the thread daemon so it ends whenever the main thread ends
    t.daemon = True
    # start the thread
    t.start()
# close client sockets
for cs in client_sockets:
    cs.close()
# close server socket
s.close()

这是发送命令的 client.py 代码：

import socket
import random
from threading import Thread
from datetime import datetime
from colorama import Fore, init, Back

# init colors
init()

# set the available colors
colors = [Fore.BLUE, Fore.CYAN, Fore.GREEN, Fore.LIGHTBLACK_EX,
    Fore.LIGHTBLUE_EX, Fore.LIGHTCYAN_EX, Fore.LIGHTGREEN_EX,
    Fore.LIGHTMAGENTA_EX, Fore.LIGHTRED_EX, Fore.LIGHTWHITE_EX,
    Fore.LIGHTYELLOW_EX, Fore.MAGENTA, Fore.RED, Fore.WHITE, Fore.YELLOW
]

# choose a random color for the client
client_color = random.choice(colors)

# server's IP address
# if the server is not on this machine,
# put the private (network) IP address (e.g 192.168.1.2)
SERVER_HOST = "127.0.0.1"
SERVER_PORT = int(input("port: ")) # server's port
separator_token = "<SEP>" # we will use this to separate the client name & message

# initialize TCP socket
s = socket.socket()
print(f"[*] Connecting to {SERVER_HOST}:{SERVER_PORT}...")
# connect to the server
s.connect((SERVER_HOST, SERVER_PORT))
print("[+] Connected.")
# prompt the client for a name
name = ""
def listen_for_messages():
    ...
# make a thread that listens for messages to this client & print them
t = Thread(target=listen_for_messages)
# make the thread daemon so it ends whenever the main thread ends
t.daemon = True
# start the thread
t.start()
while True:
    # input message we want to send to the server
    to_send = input()
    # a way to exit the program
    if to_send.lower() == 'q':
        break
    # add the datetime, name & the color of the sender
    to_send = f"{name}{separator_token}{to_send}{Fore.RESET}"
    # finally, send the message
    s.send(to_send.encode())

# close the socket
s.close()

问题是，编辑命令后，服务器理解了所需的消息，例如ls，但仍然写着没有这样的命令sh: ls: 无法访问或未找到*