On Jul 10, 4:10 pm, Guy Davidson <[EMAIL PROTECTED]> wrote: > I try to send the following message, using the socket.send() command: > > 'HTTP/1.1 200 OK\r\nDate: Thu, 10 July 2008 14:07:50 GMT\r\nServer: > Apache/2.2.8 (Fedora)\r\nX-Powered-By: PHP/5.2.4\r\nContent-Length: 4\r > \nConnection: close\r\nContent-Type: text/html; charset=UTF-8\r\n\r > \n[0]\n' > > However, when I snoop on the packets in wireshark, here's what I see: > > HTTP/1.1 200 Ok: > > HTTP/1.1 200 OK > Date: Wed, 09 July 2008 14:55:50 GMT > Server: Apache/2.2.8 (Fedora) > X-Powered-By: > > Continuation or non-HTTP traffic: > > PHP/5.2.4 > Content-Length: 4 > Connection: close > Content-Type: text/html; charset=UTF-8 > > [0] > > It splits into two packages, which the meter can't read, and the > communication breaks down there.
OK, it looks like a single TCP segment is being sent by you (which is consistent with only one socket.send() command being needed), but something along the way to the meter is using an MTU (Maximum Transmission Unit) of about 100 bytes, producing two IP datagrams. How many hops are there between the PC and the meter? Are you sniffing on the same subnet as the PC, the meter, or somewhere in between? MTU is normally set to about 1500 (and MSS is generally MTU-40), but you can generally change these values. You should be able to set the do-not-fragment flag on your IP packets, but that may cause them to get dropped instead of sent. You could also try setting a smaller ICP MSS (Maximum Segment Size), which the meter might be able to assemble, even if it can't handle fragmented IP datagrams. Try http://www.cisco.com/en/US/tech/tk870/tk877/tk880/technologies_tech_note09186a008011a218.shtml#prob_desc for more help. You really need to get a networking guru involved if you want to go down this path. I used to be one, but that was years ago. Or, you can take Gabriel Genellina's advice and try coding smaller responses. -- http://mail.python.org/mailman/listinfo/python-list
