topic Re: Problem with Telnet server in MQX Software Solutions

Problem with Telnet server

amleng — Wed, 10 Jul 2013 16:21:52 GMT

Hello all,

I need to send many small messages (less than 100 bytes) continuously like stream by Telnet protocol. I implemented a Telnet server (based on web_hvac demo). I use windows command prompt to receive the data. I think there is a problem there. I can not get all messages. Some data lost. it gets worst as it's going on. Any thought? any suggestion?

Regards,

Sina

Re: Problem with Telnet server

amleng — Wed, 10 Jul 2013 18:58:50 GMT

I send 100-byte messages every 35ms. It seems telnet works too slow or maybe buffering problem?

Re: Problem with Telnet server

amleng — Wed, 10 Jul 2013 20:26:03 GMT

i use printf() to send data over Telnet. If I increase TELNETDCFG_BUFFER_SIZE to 1024 it gets better for a few first messages and gets slow again! It seems there is a buffer issue! I'm not sure tho.

Re: Problem with Telnet server

Martin_ — Tue, 16 Jul 2013 07:19:25 GMT

MQX 4.0, right ? a small change in tcp_send.c adds TCP push flag bit into each outgoing tcp packet. comment out the 4 lines as shown below:

//if ( ((tcb->status & TCPS_TPUSH) != 0  &&
   //    GE32(tcb->sndpush, dataseq)      &&
   //    LE32(tcb->sndpush,dataseq+sent)) ||
   //   (flags & FIN))
   {
      flags |= PSH;
   } /* Endif */

Re: Problem with Telnet server

amleng — Tue, 16 Jul 2013 20:41:44 GMT

Actually, I use MQX 4.1. Those changes didn't help. no effect on the timing! Is there any other over head I can eliminate? any ACK/NACK routines? any other functions I can use to send out data over Telnet?

Re: Problem with Telnet server

Martin_ — Wed, 17 Jul 2013 06:51:01 GMT

You should attach Wireshark communication log. Windows 7 TCP stack adds 200 ms delay to ACKs, by default.

TcpAckFrequency and Nagle

Recently I worked with ethernet_serial demo (it will be in MQX 4.0.2) for transmit side it simply reads characters from UART and sends them in short TCP packets (1 byte of data payload) to a remote peer. By disabling Windows 7 TCP ACK delay I found that RTCS transmits outbound packets very fast. Just the remote application only buffers the incoming data and doesn't display them on time. By adding push flags to the outbound packets the remote application is instructed to flush the incoming buffer frequently.

Re: Problem with Telnet server

amleng — Fri, 19 Jul 2013 20:02:31 GMT

Awesome! I just did the modification on Telnet command prompt and it works pretty smooth.

Thanks martin,

Re: Problem with Telnet server

chris-quin — Tue, 20 Oct 2015 15:19:44 GMT

But why did you change it? Is there an acceptable reason? I got errors because of this.

Greetings