python-kafka源码解析之socketpair

 1 # pylint: skip-file
 2 # vendored from https://github.com/mhils/backports.socketpair
 3 from __future__ import absolute_import
 4 
 5 import sys
 6 import socket
 7 import errno
 8 
 9 _LOCALHOST    = '127.0.0.1'
10 _LOCALHOST_V6 = '::1'
11 
12 #socketpair返回本地建立连接的两端socket
13 if not hasattr(socket, "socketpair"):
14     # Origin: https://gist.github.com/4325783, by Geert Jansen.  Public domain.
15     def socketpair(family=socket.AF_INET, type=socket.SOCK_STREAM, proto=0):
16         if family == socket.AF_INET: #ipv4
17             host = _LOCALHOST
18         elif family == socket.AF_INET6: #ipv6
19             host = _LOCALHOST_V6
20         else:
21             raise ValueError("Only AF_INET and AF_INET6 socket address families "
22                              "are supported")
23         if type != socket.SOCK_STREAM:
24             raise ValueError("Only SOCK_STREAM socket type is supported")
25         if proto != 0:
26             raise ValueError("Only protocol zero is supported")
27 
28         # We create a connected TCP socket. Note the trick with
29         # setblocking(False) that prevents us from having to create a thread.
30         lsock = socket.socket(family, type, proto)
31         try:
32             lsock.bind((host, 0)) #端口0说明由系统动态创建监听端口
33             lsock.listen(min(socket.SOMAXCONN, 128))#SOMAXCONN定义了系统中每一个端口最大的监听队列的长度,这是个全局的参数,默认值为128，https://jaminzhang.github.io/linux/understand-Linux-backlog-and-somaxconn-kernel-arguments/
34             # On IPv6, ignore flow_info and scope_id
35             addr, port = lsock.getsockname()[:2]#返回这个socket的地址
36             csock = socket.socket(family, type, proto)
37             try:
38                 csock.setblocking(False)#设置socket为非阻塞模式,非阻塞模式下recv没有收到数据或send数据没有立即发送出去,则会抛出异常，等价于s.settimeout(0.0)。
39                 # 阻塞模式,会等待直到有数据或数据发送出去,等价于s.settimeout(None)
40                 if sys.version_info >= (3, 0):
41                     try:
42                         csock.connect((addr, port))
43                     except (BlockingIOError, InterruptedError):
44                         pass
45                 else:
46                     try:
47                         csock.connect((addr, port))##连接本地创建的lsock
48                     except socket.error as e:
49                         if e.errno != errno.WSAEWOULDBLOCK:
50                             raise
51                 csock.setblocking(True)#重新设置socket为阻塞模式
52                 ssock, _ = lsock.accept()#服务端socket接收连接返回和特定客户端建立连接后的新socket ssock
53             except Exception:
54                 csock.close()
55                 raise
56         finally:
57             lsock.close()#关闭监听套接字lsock
58         return (ssock, csock)#返回本地互相连接的两端socket
59 
60     socket.socketpair = socketpair