最近要直接用Socket做一個簡單的Server，想使用non-blocking的Scoket，但是遇到一些問題，解決了所以在這里總結一下。

簡單的Server端代碼片段（只有接受數(shù)據(jù)的）：

#!/usr/bin/env python
# -*- coding: UTF-8 -*-
import ssl
import select
import socket

DEFAULT_SERVER_HOST = "0.0.0.0"
DEFAULT_SERVER_PORT = 14443

class Server(object):

    def __init__(self, host, port, is_ssl=False, cert_file=None, key_file=None):
        self.host = host
        self.port = port
        self.is_ssl = is_ssl
        self.cert_file = cert_file
        self.key_file = key_file
        self.context = None

        self.__socket = None
        self.running = False
        self.multiplex = None

        self.read_set = set()
        self.write_set = set()
        self.error_set = set()

    def __initialize(self):

        if self.is_ssl and (self.cert_file is None or self.key_file is None):
            raise Exception("If you want to enable ssl, please set cert_file and key_file")

        if self.is_ssl:
            self.context = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
            self.context.load_cert_chain(certfile=self.cert_file, keyfile=self.key_file)

        self.__socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.__socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT & socket.SO_REUSEADDR, 1)

        self.__socket.bind((self.host if self.host is not None else DEFAULT_SERVER_HOST,
                            self.port if self.port is not None else DEFAULT_SERVER_PORT))

        self.__socket.setblocking(0)
        self.__socket.listen(5)

    def start(self):
        self.__initialize()

        server_fd = self.__socket.fileno()
        self.read_set.add(server_fd)

        while True:
            read_list, write_list, error_list = select.select(self.read_set, self.write_set, self.error_set, 2)

            if server_fd in read_list:
                conn, addr = self.__socket.accept()
                conn.setblocking(0)
                if self.is_ssl:
                    conn = self.context.wrap_socket(conn, server_side=True, do_handshake_on_connect=False)
                    i = 0

                    while True:
                        i += 1
                        print(i)
                        try:
                            conn.do_handshake()
                            select.select([conn], [], [])
                            break
                        except ssl.SSLError as err:
                            if err.args[0] == ssl.SSL_ERROR_WANT_READ:
                                print("read")
                                select.select([conn], [], [])
                            elif err.args[0] == ssl.SSL_ERROR_WANT_WRITE:
                                print("write")
                                select.select([], [conn], [])
                            else:
                                raise

                # rfile = conn.makefile("rb")
                # a = rfile.read(1024*8)
                a = conn.recv(1024*8)
                print(a)

if __name__ == "__main__":
    cs = Server("0.0.0.0", 14443, True, "snakeoil.crt", "snakeoil.key")
    cs.start()

由于self.__socket.setblocking(0) conn.setblocking(0)都設置為非阻塞，所以conn = self.context.wrap_socket(conn, server_side=True, do_handshake_on_connect=False) 不能設置為連接時自動握手。

在成功握手后，發(fā)現(xiàn)一個問題，調用

rfile = conn.makefile("rb")
a = rfile.read(1024*8)

如果讀取范圍較大，會出現(xiàn)

Traceback (most recent call last):
  File "/home/ming/Application/pycharm-2017.1.4/helpers/pydev/pydevd.py", line 1591, in <module>
    globals = debugger.run(setup['file'], None, None, is_module)
  File "/home/ming/Application/pycharm-2017.1.4/helpers/pydev/pydevd.py", line 1018, in run
    pydev_imports.execfile(file, globals, locals)  # execute the script
  File "/home/ming/Application/pycharm-2017.1.4/helpers/pydev/_pydev_imps/_pydev_execfile.py", line 18, in execfile
    exec(compile(contents+"\n", file, 'exec'), glob, loc)
  File "/home/ming/PycharmProjects/Test/server.py", line 86, in <module>
    cs.start()
  File "/home/ming/PycharmProjects/Test/server.py", line 80, in start
    a = rfile.read(1024*8)
  File "/home/ming/.pyenv/versions/3.5.3/lib/python3.5/socket.py", line 576, in readinto
    return self._sock.recv_into(b)
  File "/home/ming/.pyenv/versions/3.5.3/lib/python3.5/ssl.py", line 937, in recv_into
    return self.read(nbytes, buffer)
  File "/home/ming/.pyenv/versions/3.5.3/lib/python3.5/ssl.py", line 799, in read
    return self._sslobj.read(len, buffer)
  File "/home/ming/.pyenv/versions/3.5.3/lib/python3.5/ssl.py", line 583, in read
    v = self._sslobj.read(len, buffer)
ssl.SSLWantReadError: The operation did not complete (read) (_ssl.c:2090)

這個錯誤，表示讀未完成。
而使用a = conn.recv(1024*8)則不會發(fā)生錯誤。

發(fā)現(xiàn)使用makefile()后的讀操作，將會多次調用ssl.py的SSLSocket.class的recv_into方法，最后到ssl.py的SSLObject

    def read(self, len=1024, buffer=None):
        """Read up to 'len' bytes from the SSL object and return them.

        If 'buffer' is provided, read into this buffer and return the number of
        bytes read.
        """
        if buffer is not None:
            v = self._sslobj.read(len, buffer)    //makefile 后執(zhí)行這句
        else:
            v = self._sslobj.read(len)
        return v

，直至錯誤出現(xiàn)。

而直接使用socket的read方法，則是直接調用ssl.py的SSLObject的

    def read(self, len=1024, buffer=None):
        """Read up to 'len' bytes from the SSL object and return them.

        If 'buffer' is provided, read into this buffer and return the number of
        bytes read.
        """
        if buffer is not None:
            v = self._sslobj.read(len, buffer)   
        else:
            v = self._sslobj.read(len) // socket 的read執(zhí)行這句
        return v

更深入的原因還沒找出，目前覺得應該是makefile后把socket當成文件讀取，會嘗試讀直至無法繼續(xù)讀取，所以才會導致錯誤發(fā)生。