RL-ARM User's Guide

TCP Socket

The Transmission Control Protocol (TCP) is a connection oriented reliable protocol. TCP is much more complex than UDP and introduces more protocol overhead. It implements a number of protocol timers to ensure reliable and synchronized communication between the two end systems. It is thus suitable to use on WANs.

The following TCP options are configurable:

• TCP Sockets switch enables or disables the TCP Socket service in your application. It is enabled when this value is set to 1. It should be set to 0 when the TCP connections are not used.

  #define TCP_ENABLE     1
  

• Number of TCP Sockets specifies the number of available TCP sockets. This number is usually set to the maximum number of simultaneously opened TCP connections.

  #define TCP_NUMSOCKS   5
  

• Number of Retries specifies the number of retransmissions before the TCP module gives up. Data is retransmitted if it is not acknowledged within the timeout frame defined by the TCP_RETRYTOUT.

  #define TCP_MAXRETRY   5
  

• Retry Timeout in seconds is the timeout, after which the TCP module retransmits the data. This is the initial timeout value. When the data exchange is going on, the system measures the response time and corrects this timeout.

  #define TCP_RETRYTOUT  4
  

• Default Connect Timeout in seconds is the default Keep Alive timeout. After this timeout has expired, the TCP link is disconnected. This parameter is used by applications like HTTP Server and Telnet Server.

  #define TCP_DEFTOUT    120
  

• Maximum Segment Size specifies the maximum number of bytes in the TCP segment's data field. Acceptable values for this parameter are in the range from 536 to 1460 bytes. The default value for ethernet network is 1460 bytes.

  #define TCP_MAXSEGSZ   1460
  

• Receive Window Size specifies the amount of data the socket is able to buffer. The default value is 4380 bytes.

  #define TCP_RECWINSZ   4380
  

Note

• When the TCP Sockets are not enabled, the ARM linker does not link the TCP support modules to your application and thus reduces the code size and memory usage.