Can't send message from python server to java client

Question

I try to create a client/server application between my Raspberry Pi (server in Python) and a java Client over my local network.

I can't figure out how to send message from the Python server to the Java client. I always have the error : [Errno 32] Broken pipe.

I can't seen where I'm wrong.

Here the Server code :

class ServerLED():
'''
classdocs
'''
def __init__(self, port = 15555):
 '''
 Constructor
 '''
 self.socketPi = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
 self.socketPi.bind(("", port))
 self.response = ""
def listening(self):
 self.socketPi.listen(5)
 self.client, self.address = self.socketPi.accept()
 print "{} connected".format( self.address )
def receivingMessage(self):
 self.response = self.client.recv(1024)
 if self.response != "":
 print self.response
def answer(self):
 messageTosend = "Echo \r\n"
 try:
 self.socketPi.send(messageTosend)
 except socket.error, e:
 print "error is ", e
 self.socketPi.close()

I use the function this way :

socketPi = Server.ServerLED()
print "listening..."
socketPi.listening()
print "sending message..."
socketPi.answer()
print "done"
socketPi.receivingMessage()

On the client side (in JAVA) :

Socket socket = new Socket("192.168.1.18", 15555);
System.out.println("SOCKET = " + socket);
PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
BufferedReader in = new BufferedReader(
new InputStreamReader(socket.getInputStream()));
str = in.readLine(); // Reding "ECHO"
System.out.println(str); 
out.println("Hello"); // sending message

I'm always stuck in the first "send()" of the server. If I start by sending a message from the client to the server, the server reads it but fails to respond.

Server output :

Start python for LED
listening...
('192.168.1.13', 58774) connected
sending message...
error is [Errno 32] Broken pipe

Does someone know where I am wrong ? Thanks a lot.

Maxime.

• Marco: I have written something similar to your python server recently and I used a python module called asynchat it was quite easy to implement. docs.python.org/2/library/asynchat.html

Answer 1

It is a strange setup generally, but in the server you should be sending on the connection socket (self.client), not on the listening socket (self.socketPi).

Answer 2

One problem is that the Socket you create in java isn't bind, that is - the Socket object is just created, but not opened waiting for the raspberry pi incoming socket connection.

Add the row

socket.bind(new java.net.InetSocketAddress("192.168.1.18", 15555));

after the socket is created. The address in the Socket constructor is probably not nescessary.