Python 为什么客户只有在发送邮件后才收到？

为什么客户只有在发送邮件后才收到？当我启动服务器并连接两个客户端时，它们应该能够相互发送消息。他们会这样做，但只有当他们当前已向服务器发送消息时才会这样做。不应该如此，因为发送和接收在不同的线程中

客户端：

import socket
import threading

HEADER = 64
PORT = 5050
FORMAT = 'utf-8'
DISCONNECT_MESSAGE = "!DISCONNECT"
SERVER = "my local IP"
ADDR = (SERVER, PORT)

client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
client.connect(ADDR)


def send(msg):
    message = msg.encode(FORMAT)
    msg_length = len(message)
    send_length = str(msg_length).encode(FORMAT)
    send_length += b' ' * (HEADER - len(send_length))
    client.send(send_length)
    client.send(message)

def events():
    while True:
        msg = input()
        if msg == "quit":
            send(DISCONNECT_MESSAGE)
            break
        else:
            send(msg)

def recieve():
    while True:
        msg_length = client.recv(HEADER).decode(FORMAT)
        if msg_length:
            msg_length = int(msg_length)
            msg = client.recv(msg_length).decode(FORMAT)
            print(msg)

thread1 = threading.Thread(target=events)
thread2 = threading.Thread(target=recieve)
thread1.start()
thread2.start()

服务器端：

import socket
import threading

HEADER = 64
PORT = 5050
SERVER = socket.gethostbyname(socket.gethostname())
ADDR = (SERVER, PORT)
FORMAT = 'utf-8'
DISCONNECT_MESSAGE = "!DISCONNECT"

server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.bind(ADDR)

messages_to_send = {}
client_pairs = []
new_client = False


def send(msg, conn):
    message = msg.encode(FORMAT)
    msg_length = len(message)
    send_length = str(msg_length).encode(FORMAT)
    send_length += b' ' * (HEADER - len(send_length))
    conn.send(send_length)
    conn.send(message)


def handle_client(conn, addr):
    global new_client
    if new_client:
        print(f"[NEW CONNECTION] {addr} connected to {new_client}")
        client_pairs.append((new_client, addr))
        new_client = False
    else:
        print(f"[NEW CONNECTION] {addr} waiting")
        new_client = addr
    connected = True
    while connected:
        msg_length = conn.recv(HEADER).decode(FORMAT)
        if msg_length:
            msg_length = int(msg_length)
            msg = conn.recv(msg_length).decode(FORMAT)
            if msg == DISCONNECT_MESSAGE:
                print(f"[DISCONNECTED] {addr}")
                connected = False
                if new_client == addr:
                    new_client = False
                else:
                    for pair in client_pairs:
                        if addr == pair[0]:
                            if new_client:
                                client_pairs.append((new_client, addr))
                                new_client = False
                            else:
                                new_client = pair[1]
                            break
                        elif addr == pair[1]:
                            if new_client:
                                client_pairs.append((new_client, addr))
                                new_client = False
                            else:
                                new_client = pair[0]
                            break
            else:
                for pair in client_pairs:
                    if addr == pair[0]:
                        messages_to_send[pair[1]] = msg
                    elif addr == pair[1]:
                        messages_to_send[pair[0]] = msg
            print(f"[{addr}] {msg}")
        if addr in messages_to_send.keys():
            send(messages_to_send[addr], conn)
            del messages_to_send[addr]

    conn.close()


def start():
    server.listen()
    print(f"[LISTENING] Server is listening on {SERVER}")
    while True:
        conn, addr = server.accept()
        thread = threading.Thread(target=handle_client, args=(conn, addr))
        thread.start()
        print(f"\n[ACTIVE CONNECTIONS] {threading.activeCount()-1}")


print("[STARTING] Server is starting...")
start()