又说到之前Murder的一个python输出结果引发的深入分析： 前几天测试Murder时，当没开启Tracker服务器时，在Peer下执行下载时会有如下报错：

[root@xxx_game dist]# python /usr/local/murder/dist/murder_client.py peer /data/download/server_1262.zip.torrent /data/download/server_1262.zip x.x.x.x
Problem connecting to tracker - [Errno 111] Connection refused

提示已经很明显示了，不能连接到tracker，事实也是如此，我把tracker进程给关了。 起初我以为[Errno 111] Connection refused是作者自己定义的错误码， 在源码里搜索Errno 111 Connection refused，并没有搜索到相关代码。

然后查了下，

exception socket.error

This exception is raised for socket-related errors. The accompanying value is either a string telling what went wrong or a pair (errno, string) representing an error returned by a system call, similar to the value accompanying os.error. See the module errno, which contains names for the error codes defined by the underlying operating system.

module-errno

This module makes available standard errno system symbols. The value of each symbol is the corresponding integer value. The names and descriptions are borrowed from linux/include/errno.h, which should be pretty all-inclusive.

当python执行脚本时连接Track时，最终是系统创建sokcet去连接，这个过程中出错了，系统给出errno和提示。 “[Errno 111] Connection refused”这个提示是系统给出来的。 通过 man errno.h和python中的输出可以验证：

ECONNREFUSED
       Connection refused.

>>> import errno;
>>> print errno.ECONNREFUSED
111

Ref

socket — Low-level networking interface
errno — Standard errno system symbols