Keep connection open? about ethercard HOT 4 CLOSED

This is not possible - the code only supports single-packet sends in its original design, but there is a patch by Andrew Lindsay to handle incoming MP3 streams, which would indicate that multi-packet receives might be possible through a suitably modified version of the EtherCard library. Try googling for "thiseldo" and "mp3".

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Looking at the code, it seems that the file tcpip.cpp, line 622 - 623 has a comment to say:

  // Comment out to enable large files, e.g. mp3 streams to be downloaded

// tcp_client_statete = 4;

however this is commented out in the library and also looks like it should be 'tcp_client_state' not 'tcp_client_statete'.
For normal operation this should be present, to allow large files to be received it should be commented out, e.g. if receiving a stream from a server.

I think this however is different to what you are asking, server push is different to client get, which this change allows.

JCW - I think the line needs to be uncommented and corrected otherwise you could be seeing issues with connections being kept open.

Thanks

Andy
(from a tent in France!)

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Jean-Claude, thanks for the information.

Andy, you are right, I am asking about having the server to ping the device every so often in order to get a sensor reading as opposed to having to have the device constantly pinging the server. I understand that there are other firewall/keep-alive issue with this change but that is OK.

To follow up on your comment. If I uncomment line 623 (and fix the typo), this will allow the connection to go into "State 4" and prevent it from going to "State 5", which I think is "closed". Are there any other modifications that will be needed? Will the device then keep the connection open until the server closes it or the firewall closes the connection?

Also, I'm trying to figure out what the different states are. My current hypothesis is:

State 1: Unconnected
State 2: Handshake established
State 3: Transmitting
State 4: Keep-alive
State 5: Closed

Thanks again for the information you guys. Also, this library has been wonderful and very easy to get started with. Thank you!

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@thiseldo Thanks again for the tip. I'm exploring it more now but am a little confused about what I have to do on the server side to trigger the code into that state 4. The tools I'm using are node.js and chunked transfer encoding.

My understanding so far is that packetLoop gets a packet. Then it is looking at the packet to make sure it is larger than a certain size. My confusion comes with line 607,

len = (*client_tcp_datafill_cb)((gPB[TCP_SRC_PORT_L_P]>>5)&0x7);

I can't figure out what it is trying to do. It seems like if I can get this to be >0 I will pass the if statement on line 621 ,

if (tcp_client_state==3 && len>0) { 
  // Comment out to enable large files, e.g. mp3 streams to be downloaded
    tcp_client_state = 4;

which will keep the connection open.

What does the server have to respond in order for it to get into this area of the code?

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