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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

Ethernet Interface

The IP address for the ethernet network interface is assigned in several ways using the following modes:

  • Dynamic Host Configuration
    This mode is mostly used. It requires a centralized DHCP server in the LAN network. DHCP server maintains a database of leased IP addresses, and assigns to the client an unused IP address. It specifies also a network mask and a default gateway to use, when the system wants to access the internet. The DHCP server specifies also a primary and optional secondary DNS server. The DNS server is used to resolve the IP address for a known host name. In order to use this mode, the option Dynamic Host Configuration must be enabled in the system configuration.
  • AutoIP
    The system first tries the DHCP mode, and if it fails after a timeout of 60 seconds, the system starts an auto-configuration mode. It randomly selects an IP address and checks, if it is in use. If the chosen IP address is not used, the system starts using it. Otherwise the system tries a different random IP address. In this mode an IP address and network mask are assigned. The default gateway is not assigned, because it is not known. Connecting to internet is thus not possible from the AutoIP mode. The IP address is picked from the link-local IP address block ( - The network mask is
  • Static IP
    The IP address, network mask and default gateway are configured in the system configuration file. It is possible to change the IP address at runtime. The static configuration specifies also a primary and optional secondary DNS server.


  • In AutoIP mode, a DHCP client is still trying to obtain an IP address every 120 seconds. On success the IP address is re-assigned. The system then starts using a new, DHCP assigned IP address and the mode is changed back to DHCP mode. The AutoIP mode is an extension of the Dynamic Host Configuration mode.
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