我在python中使用REQ / REP类型套接字进行ZMQ通信.有多个客户端尝试连接到一个服务器.客户端脚本中添加了超时以防止无限期等待.
问题是当服务器没有运行,并且客户端试图建立连接时,它的消息会被添加到队列缓冲区中,理想情况下,此时该队列缓冲区甚至不应该存在.当脚本开始运行并且新客户端连接时,服务器首先获取先前客户端的数据.这不应该发生.
当服务器启动时,它假定客户端已连接到它,因为它曾尝试连接,并且无法干净地退出(因为服务器已关闭).
在下面的代码中,当客户端第一次尝试时,它会获得ERR 03:服务器关闭,这是正确的,然后是错误断开连接.当服务器启动时,我得到连接的第一个客户端的ERR 02:Server Busy.这不应该发生.客户端应该能够在服务器启动并运行时与服务器无缝连接.
服务器代码:
import zmq
def server_fn():
context = zmq.Context()
socket = context.socket(zmq.REP)
socket.bind("tcp://192.168.1.14:5555")
one=1
while one == 1:
message = socket.recv()
#start process if valid new connection
if message == 'hello':
socket.send(message) #ACK
#keep session alive until application ends it.
while one == 1:
message = socket.recv()
print("Received request: ", message)
#exit connection
if message == 'bye':
socket.send(message)
break
#don't allow any client to connect if already busy
if message == 'hello':
socket.send ('ERR 00')
continue
#do all data communication here
else:
socket.send('ERR 01: Connection Error')
return
server_fn()
客户代码:
import zmq
class client:
def clientInit(self):
hello='hello'
#zmq connection
self.context = zmq.Context()
print("Connecting to hello world server...")
self.socket = self.context.socket(zmq.REQ)
self.socket.connect("tcp://192.168.1.14:5555")
#RCVTIMEO to prevent forever block
self.socket.setsockopt(zmq.RCVTIMEO, 5000)
#SNDTIME0 is needed since script may not up up yet
self.socket.setsockopt(zmq.SNDTIMEO, 5000)
try:
self.socket.send(hello)
except:
print "Sending hello failed."
try:
echo = self.socket.recv()
if hello == echo:
#connection established.
commStatus = 'SUCCESS'
elif echo == 'ERR 00':
#connection busy
commStatus = "ERR 00. Server busy."
else:
#connection failed
commStatus="ERR 02"
except:
commStatus = "ERR 03. Server down."
return commStatus
def clientQuit(self):
try:
self.socket.send('bye')
self.socket.recv()
except:
print "Error disconnecting."
cObj = client()
commStatus=cObj.clientInit()
print commStatus
cObj.clientQuit()
PS – 我觉得解决方案可能在于正确使用socket.bind和socket.connect.
解决方法:
回答我自己的问题 –
问题是第一个客户端在开始运行时发送服务器接受的消息,而不管客户端的状态如何.
为了防止这种情况,必须做两件事.最重要的是使用socket.close()来关闭客户端连接.其次,LINGER参数可以设置为低值或零.这将在套接字关闭后的超时值之后清除缓冲区.
class client:
def clientInit(self):
...
self.socket.setsockopt(zmq.LINGER, 100)
...
def clientQuit(self):
try:
self.socket.send('bye')
self.socket.recv()
except:
print "Error disconnecting."
self.socket.close()