asDexy - Telnet Proxy Server

Dexy is a Proxy Server maintaining Telnet sessions when the mobile Telnet clients get out of radio area or the connection gets lost for other reasons (e.g. because the client went into sleep mode or a battery had to be changed). Dexy keeps the TCP connection to the host. As soon as the client establishes a new connection, it will be linked with the old session.

Mode of operation:

  • A new client connects to Dexy Proxy Server instead of the host directly
  • Dexy establishes a new connection to the host
  • All data will be forwarded in both directions
  • In case the connection between client and Dexy gets lost or shutdown by the client, Dexy will keep the connection to the host
  • When a new connection to Dexy is established by the same client, Dexy recognizes that a session exists and forwards the Data between the new client-to-Proxy- and the old Proxy-to-host connection
  • Optionally, Dexy can send a refresh telegram to the host on reconnection of the client, in order to induce the host to re-send the current session screen
  • The time a session is maintained is configurable

System requirements:

  • Microsoft Windows Server 2012
  • Microsoft Windows Server 2008 / 2008 R2
  • Microsoft Windows Server 2003
  • Other Win32 systems (XP, Windos 7, Windows 8)


  • Dexy is installed as a service, either on the same or on a different computer as the Telnet host
  • Allows several tousands of concurrent connections
  • Supports all major Telnet emulations (VT100, VT220, IBM5250, IBM3270) and other TCP connections not based on Telnet
  • Identification of a clients by its IP address (alternatively by other attributes)
  • Installable in virtual envirenments (e.g. Hyper-V)
  • Little system requirements (depending on the number of concurrent connections)
  • Logging of the operation
  • Can capture the data flow of single or all clients to files for analysis

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