服务器可以在没有配置 IP 的情况下监听 UDP 消息吗

Question

请看下面的python代码。 我创建了一个 Server 类来监听 10000 端口以接收 UDP 广播消息。

如果系统中配置了IP地址，则可以接收UDP广播消息。如果没有配置 ip 地址，则无法接收任何消息。

你能告诉我为什么吗？

import socket
import sys

class Server:

    class Handler:

        def handle(self, message):
            pass

        def __init__(self, serialNo):
            self.serialNo = serialNo

        def _setAddress(self, socket, message, address):
            self.message = message
            self.address = address
            self.socket = socket

        def send(self, message):
            self.socket.sendto(message, self.address)

        def getSerialNo(self):
            return self.serialNo

    def __init__(self, port, handler):
        self.ss = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
        self.ss.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        self.ss.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
        self.handler = handler

        try:
            self.ss.bind(('<broadcast>', port))
        except:
            self.ss.close()
            raise RuntimeError("Create socket error")
        self.ss.setblocking(1)

    def loop(self):
        while True:
            try:
                print "Listening for broadcast..."
                message, address = self.ss.recvfrom(8192)
                print "Got request from %s:%s" % (address, message)
                self.handler._setAddress(self.ss, message, address)
                self.handler.handle(message)
            except (KeyboardInterrupt, SystemExit):
                raise
            except:
                sys.exc_info()[0]

Answer 1

参考pydhcp客户端代码后，我做了如下改动：

import socket
import sys
import select

class Server:

    class Handler:

        def handle(self, message):
            pass

        def __init__(self, serialNo):
            self.serialNo = serialNo

        def _setAddress(self, socket, message, address):
            self.message = message
            self.address = address
            self.socket = socket

        def send(self, message):
            self.socket.sendto(message, self.address)

        def getSerialNo(self):
            return self.serialNo

        def __init__(self, port, handler):
            self.ss = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
            self.ss.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
            self.ss.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
            self.handler = handler

        try:
            self.ss.bind(("0.0.0.0", int(port)))
        except:
            self.ss.close()
            raise RuntimeError("Create socket error")

        def loop(self):
            while True:
            try:
                print "Listening for broadcast..."
                data_input,data_output,data_except =    select.select([self.ss],[],[], 60)
            if (data_input != []):
               (message, address) = self.ss.recvfrom(2048)
               print "Got request from %s:%s" % (address, message)
               self.handler._setAddress(self.ss, message, address)
               self.handler.handle(message)
            else:
               print "no data within 60 seconds"
        except (KeyboardInterrupt, SystemExit):
            raise
        except:
            sys.exc_info()[0]

现在可以接收广播包了，但是在RedHat上就不行了。