只有在python套接字中可用時纔會收到數據

Question

我只想在可用時接收數據。如Arduino中的Serial.available()。我想要這樣的代碼：

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

事實上，我不希望程序停止只是爲了接收數據。

Answer 1

select.select可用於輪詢套接字是否有數據。這裏有一個簡單的例子：

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

例子，其中兩個客戶端連接，送東西，斷開：

('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> 

您也可以撥打.setblocking(0)一個插座上，但你必須處理異常，當你.accept()或例如：

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