pythonrecvfrom函数详解_Python总结之recv与recv_from

在udp编程中&＃xff0c;会发现&＃xff0c;在利用socke接收数据时用的时recv_from&＃xff0c;在tcp编程中用的是recv。

但是&＃xff0c;细心的你会发现&＃xff0c;udp中接收端口的时recv_rom&＃xff0c;在tcp中则是accept&＃xff0c;为什么呢&＃xff1f;

因为recv的recvfrom是可以替换使用的&＃xff0c;只是recvfrom多了两个参数&＃xff0c;可以用来接收对端的地址信息&＃xff0c;这个对于udp这种无连接的&＃xff0c;可以很方便地进行回复。下面是源码&＃xff1a;

def recvfrom(self, *args):

if self._sslobj:

raise ValueError("recvfrom not allowed on instances of %s" %

self.__class__)

else:

return socket.recvfrom(self, *args)

而换过来如果你在udp当中也使用recv&＃xff0c;那么就不知道该回复给谁了&＃xff0c;如果你不需要回复的话&＃xff0c;也是可以使用的。另外就是对于tcp是已经知道对端的&＃xff0c;就没必要每次接收还多收一个地址&＃xff0c;没有意义&＃xff0c;要取地址信息&＃xff0c;在accept当中取得就可以加以记录了。下面是源码&＃xff1a;

def accept(self):

"""accept() -> (socket object, address info)

Wait for an incoming connection. Return a new socket

representing the connection, and the address of the client.

For IP sockets, the address info is a pair (hostaddr, port).

"""

fd, addr &＃61; self._accept()

# If our type has the SOCK_NONBLOCK flag, we shouldn&＃39;t pass it onto the

# new socket. We do not currently allow passing SOCK_NONBLOCK to

# accept4, so the returned socket is always blocking.

type &＃61; self.type & ~globals().get("SOCK_NONBLOCK", 0)

sock &＃61; socket(self.family, type, self.proto, fileno&＃61;fd)

# Issue #7995: if no default timeout is set and the listening

# socket had a (non-zero) timeout, force the new socket in blocking

# mode to override platform-specific socket flags inheritance.

if getdefaulttimeout() is None and self.gettimeout():

sock.setblocking(True)

return sock, addr

这里可以看到retrun的返回值有两个&＃xff0c;一个sock&＃xff0c;一个addr。