How to Transfer Files Using INTERLNK in MS-DOS 6.22

The INTERLNK utility in MS-DOS 6.22 facilitates direct file transfers and resource sharing between two computers connected through serial or parallel ports. Operating on a client-server architecture, it redirects drive letters and printer ports from a host system to a client system, allowing users to browse, copy, and execute files across the connection using standard DOS commands.

The Client-Server Architecture

INTERLNK relies on two distinct components: a client device driver (INTERLNK.EXE) and a server-side executable (INTERSVR.EXE).

  • The Server (INTERSVR.EXE): The computer containing the source files or drives runs this program from the command line. While INTERSVR is active, the server machine is dedicated exclusively to handling requests from the client.
  • The Client (INTERLNK.EXE): The receiving computer loads INTERLNK.EXE via its CONFIG.SYS configuration file. The driver manages the local drive letter assignments and intercepts input/output operations, routing them to the server over the cable.

Required Hardware and Connections

Data transmission requires a physical cable connecting the communication ports of both machines. INTERLNK supports two primary cable types:

  • Parallel Cable (Bidirectional/LapLink): Uses standard DB-25 parallel (LPT) ports. This method provides the fastest transfer speeds.
  • Serial Cable (Null-Modem): Uses RS-232 serial (COM) ports with crossed receive and transmit lines (9-pin or 25-pin). While slower than parallel, it is functional over longer distances.

Configuring the Client PC

To enable drive redirection, the client PC must load the driver at boot time. This is done by adding the following line to the client's CONFIG.SYS file:

DEVICE=C:\DOS\INTERLNK.EXE

Optional parameters can be appended to the command. For example, /DRIVES:n specifies the number of redirected drives to allocate, while /NOPRINTER disables printer port redirection to conserve conventional memory.

After editing CONFIG.SYS, the client computer must be rebooted. Upon startup, MS-DOS assigns new logical drive letters to represent the remote drives that will be provided by the server.

Starting the Server PC

With the connection cable attached to both PCs, the server machine must launch the server software from the DOS prompt:

INTERSVR

INTERSVR automatically scans available COM and LPT ports to detect the client connection. Once established, the server displays a split-screen status interface detailing:

  • The active port connection (e.g., LPT1 or COM1).
  • The port transfer rate.
  • The mapping table showing which local server drive letters correspond to the assigned drive letters on the client PC.

Executing File Transfers

Once the connection is active, the user performs all file operations entirely from the client machine. The remote drives appear as local drives in the MS-DOS environment.

For instance, if the server’s C: drive is mapped to E: on the client, standard DOS utilities function transparently across the cable:

  • View remote files: DIR E:
  • Copy files from server to client: COPY E:\DATA\FILE.TXT C:\BACKUP\
  • Copy files from client to server: COPY C:\DOCS\REPORT.DOC E:\REPORTS\
  • Mirror entire directory structures: XCOPY E:\PROJECT C:\PROJECT /S

Ending the Session

Because the server system cannot run other programs while INTERSVR is running, the session must be closed to return the server to normal operation. Pressing Alt+F4 on the server terminates INTERSVR and releases both the serial or parallel port and the server's local control. The client retains its assigned drive letters, but attempts to read or write to them will result in an "Abort, Retry, Fail?" error until the server is restarted.