仅在Python套接字中接收数据（如果可用）

Question

我只想在有可用数据的情况下接收数据。就像 Arduino 中的

Serial.available()

一样。我想要这样的代码：

if there is data:
     receive and print
else:
     print 'No data'

事实上，我不希望程序只是为了接收数据而停止。

Answer 1

您还可以在套接字上调用

.setblocking(False)

来禁用阻塞模式。当调用否则会阻塞时，它将引发

BlockingIOError

。但是，当您在套接字上

.accept()

或

.recv()

并且没有准备好连接或没有数据可接收时，您必须处理异常。例如：

try:
    data = s.recv(1024)
    print(data)
except BlockingIOError:
    print('no data')

select.select

可用于轮询多个套接字以获取数据。这是一个简单的例子：

import socket
import select

server = socket.socket()
server.bind(('', 8000))
server.listen()
readables = [server] # list of readable sockets.  server is readable if a client is waiting.
i = 0
while True:
    # to_read will be a list of sockets with readable data
    to_read, to_write, errors = select.select(readables, [], [], 0)
    for sock in to_read: # iterate through readable sockets
        if sock is server: # is it the server?
            client, address = server.accept()
            print(f'\r{address}: connected')
            readables.append(client) # add the client
        else:
            # read from address client
            data = sock.recv(1024)
            if not data:
                print(f'\r{sock.getpeername()}: disconnected')
                readables.remove(sock)
                sock.close()
            else:
                print(f'\r{sock.getpeername()}: {data}')
    # a simple spinner to show activity
    i += 1
    print(r'/-\|'[i%4], end='\r', flush=True)

两个客户端连接、发送内容然后断开连接的示例：

('127.0.0.1', 2983): connected
('127.0.0.1', 2983): b'hello'
('127.0.0.1', 2985): connected
('127.0.0.1', 2985): b'there'
('127.0.0.1', 2983): disconnected
('127.0.0.1', 2985): disconnected
<spinner activity here>