在智能家居项目hestia中，遇到一个关于python socket编程的小问题。发现在python socket客户端一端，在服务端断开时，没有抛出异常。

[code lang=”python”]
try:
msg = _sFile.readline()
except socket.error, e:
logging.info("socket exception" + e.message)
_reconnect()
[/code]

翻阅文档后，发现python socket分为阻塞式和非阻塞式。默认初始化的socket是阻塞式的，在阻塞式下，如果socket断开链接，将会返回空串。官方解释如下：

socket.setblocking(flag)

Set blocking or non-blocking mode of the socket: if flag is 0, the socket is set to non-blocking, else to blocking mode. Initially all sockets are in blocking mode. In non-blocking mode, if a recv() call doesn’t find any data, or if a send() call can’t immediately dispose of the data, an error exception is raised; in blocking mode, the calls block until they can proceed. s.setblocking(0) is equivalent to s.settimeout(0.0); s.setblocking(1) is equivalent to s.settimeout(None).

故修改代码如下：

[code lang=”python”]
try:
msg = _sFile.readline()
if msg == "":
_reconnect()
except socket.error, e:
logging.info("socket exception" + e.message)
_reconnect()
[/code]

文章来源：胡小旭 => Python socket网络编程之阻塞与非阻塞模式