Steve Horsley schreef: > [EMAIL PROTECTED] wrote: > > Dear newsgroup, > > > > I give up, I must be overseeing something terribly trivial, but I can't > > get a simple (Java) applet to react to incoming (python) SocketServer > > messages. > > > > Without boring you with the details of my code (on request available, > > though), here is what I do : > > > > I have a TCPServer and BaseRequestHandler . > > Connecting via telnet : everything goes OK. > > > > Connecting from Applet : > > problem 1 (worked around it) : java has some 'propietary' UTF-8 format, > > python's unicode doesn't seem to handle it correctly and I have to > > strip the first two bytes/chars , then all goes OK . > > > > Those 2 bytes are important! They are a string length indicator. > Here are the docs that tell you that it puts a 2-byte length on > the front: > http://java.sun.com/j2se/1.5.0/docs/api/java/io/DataOutputStream.html#writeUTF(java.lang.String) > If you are ignoring these bytes, then how can you be sure you > have received the whole string? Please don't tell me you "just > hope" that the whole string will always arrive in a single read() > call. There is no guarantee of that. TCP does NOT have message > boundaries, and TCP packets can be both fragmented and coalesced.
Ah, I see... I worked around this (see below), the workaround is consistent with what you assume. My question "How to send/receive between python SocketServer and java Applet (SocketListener)" then seems to be boiling down to: "How to interface between python unicode and java read/writeUTF?" > > Probably the same problem. If you didn't send a 2 byte length > indicator first, then java's readUTF() will have tried to > interpret the first 2 bytes that you did actually send as the > string length, and may well simply be waiting patiently for the > rest to arrive. > I just couldn't get read/writeUTF and python unicode to interface, so I refactored the applet's socketlistener to convert the socket.getInputStream to a BufferedInputReader on which I call the readline() method. I still skip the first two bytes in the python receiver which seems harmless since python doesn't use the byte length. On both sides I have other way to know when the end-of-message has been reached. A timeout mechanism provides some safety for partial transmission handling. Thanks ! Thijs -- http://mail.python.org/mailman/listinfo/python-list
