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RL-ARM User's Guide (MDK v4)

RL-RTX RL-FlashFS RL-TCPnet TCP Socket Opening TCP Connection TCP Active Open TCP Passive Open Sending TCP Data Example for Sending Data Multiple TCP Connections UDP Socket Opening UDP Connection Sending UDP Data When DHCP Enabled When ARP Cache Empty Example for Sending Data IP Multicasting Multiple UDP Connections Configuring RL-TCPnet Static Configuration System Definitions Ethernet Network Interface PPP Network Interface SLIP Network Interface UDP Socket TCP Socket BSD Socket HTTP Server Telnet Server TFTP Server TFTP Client FTP Server FTP Client DNS Client SMTP Client SNMP Agent SNTP Client Error Function Runtime Configuration Library Files Using RL-TCPnet Stand Alone With RTX Kernel Event Driven Operation IP Address Assignment Ethernet Interface PPP Interface SLIP Interface Localhost Applications HTTP Server Script Language CGI Functions Ajax Support Using XML XML Example How it works SOAP Support SOAP Interface Large POST Messages Web Pages Default Page Error Pages Web on SD Card Web Update File System Interface Http Caching How it works Internal Web External Web Multi-user Authentication Using RAM File System FCARM File Converter PRINT Directive NOPRINT Directive PAGEWIDTH Directive PAGELENGTH Directive ROOT Directive Telnet Server Command Line Interface Multi-user Authentication Sending Reply Message Short Reply Long Reply Continuous Screen Update TFTP Server File System Interface TFTP Client File System Interface FTP Server File System Interface Multi-user Authentication Supported Commands FTP Client File System Interface SMTP Client SNMP Agent MIB Database MIB Interface MIB Entry MIB Table DNS Resolver Starting DNS Device Drivers Ethernet Driver Interrupt Mode Modem Driver Serial Driver Using Serial Link Cable Connection Modem Connection Windows Dial-up Add Direct Serial Link New Dial-up Connection Configure PPP Dial-up Configure SLIP Dial-up Debugging Enabling Debug Debug Level Redirecting Output Function Overview BSD Routines CGI Routines Ethernet Routines FTP Routines HTTP Routines IGMP Routines Miscellaneous Routines Modem Routines PPP Routines Serial Routines SLIP Routines SMTP Routines SNMP Routines System Functions TCP Routines Telnet Routines TFTP Routines UDP Routines RL-CAN RL-USB Example Programs Library Reference Appendix

Stand Alone

RL-TCPnet is designed as a stand alone TCP/IP Operating System. This means it does not need any external RTOS or File System to run. It has an integrated tiny task scheduler that manages timeouts, events, and internal tasks. Each application (TCP, UDP, and Network Interface) is treated as a separate internal task.

A framework for a stand alone application basically needs to call a few system functions:

  • init_TcpNet function needs to be called after the system starts to initialize the OS.
  • init_user is the function that initializes your application. It can be placed before or after the call to init_TcpNet. If you call your initialization code before calling init_TcpNet, you cannot call any OS function from your init function (because the OS is not yet initialized).
  • main_TcpNet function needs to be called frequently to properly handle system events and timeouts. It is normally placed in an endless loop.
  • main_user is the main thread of your application. You must design it as a state machine. On each call to this function, events and timeouts must be processed according the current state of the application, and then the function should return. It should never run in an endless loop waiting for a event as this blocks the whole OS, and the system might stop functioning.
  • timer_tick function is needed to generate timer ticks for the OS. This function can be called from the function that polls for the timer timeout or from a timer interrupt function. It is used to synchronize internal timeout processing to a system tick timer. It is very important that this function be called at regular time intervals.

Here is a framework for a stand alone application:

#include <RTL.h>

static void timer_poll () {

  if (T1IR & 1) {
    T1IR = 1;
    /* Timer tick every 100 ms */
    timer_tick ();

void main (void) {

  init_TcpNet ();
  init_user ();

  while (1) {
    /* Poll for a system tick timer overflow. */
    timer_poll ();
    main_TcpNet ();
    /* A function call to your application. */
    main_user ();


  • Avoid using waiting loops in your application because the RTL-TCPnet system is blocked if any application function runs in a loop.
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