Transfer Protocols

A file transfer protocol is a set of rules that two computers follow for transferring files between them. Files can be transferred only when both computers use the same protocol. Protocols can specify error-checking and correction rules to ensure that the information you're transferring is accurately sent and received. Reflection supports several file transfer protocols:

  • Reflection 7-bit and 8-bit WRQ/Reflection protocol to HP 3000 hosts (PCLINK2), VMS hosts (VAXLINK2), and to UNIX hosts (UNXLINK2)
  • The FTP public domain protocol
  • Zmodem public domain protocol
  • Kermit public domain protocol
  • Xmodem public domain protocol

If you use SuperKermit, Kermit, Zmodem, or Xmodem, that protocol must be available on the host, and you must start the host side of the process to transfer files.

On bulletin boards, you must issue a download or upload command before starting the transfer in Reflection.

WRQ/Reflection

The WRQ/Reflection protocol requires that the appropriate host program be on the host. These host programs include PCLINK2 on an HP 3000, VAXLINK2 on a VMS host, (including OpenVMS and Alpha computers), or UNXLINK2 for a UNIX host. The WRQ/Reflection protocol offers the following features:

  • Wildcard transfers can be performed in either direction.
  • CRC-CCITT error checking is used to ensure error-free transmission. Using this method, blocks are retransmitted, if necessary, to ensure completely accurate transmission.
  • When you transfer a host file, all the file parameters of the host can be kept on the PC copy. This information can later be used to create an exact copy of the original file on the host.
  • You can specify data translation parameters and many file transfer settings in the Transfer Settings dialog box.
  • Data compression techniques produce faster transfers.

When Reflection is using the fast file transfer capability, data compression is not used because it usually slows down the file transfer.

  • ASCII files can be sent from the PC to a host printer.
  • When you click the Attributes button on the WRQ tab in the Transfer Settings dialog box or on the Filter tab, you can specify date/time filters (which limit the selection of files transferred using wildcards) or the file attributes for sending PC files and receiving host files.

FTP

File Transfer Protocol (FTP) is a public domain file transfer protocol used for file transfers to and from an FTP server. Because you can connect to an FTP server without an account, FTP servers can be useful to exchange a variety of files, including software upgrades and utilities.

Use FTP when you need network-speed file transfer across a terminal connection to a UNIX, HP 3000, VMS, or Unisys host.

If you will be using FTP exclusively for transferring files, use the Reflection FTP Client shipped with Reflection products. This application provides quick FTP transfers with a full complement of features.

Zmodem

Zmodem is a public domain file transfer protocol that uses a 32-bit CRC (cyclic redundancy check) to detect transmission errors. It also allows for the batch transfer of more than one file, time and date stamping, and automatic downloading. The Zmodem protocol is often used for downloading and uploading files from bulletin boards.

Kermit

Kermit is a public domain file transfer protocol available for many types of computers. You can transfer files between a PC and a host running Kermit protocol. If the Kermit program on your host has a server mode, you can also use this mode to transfer files.

SuperKermit

The SuperKermit protocol offers the following enhanced features over the standard Kermit protocol:

  • You can set packet sizes greater than 94 bytes; the new default value is 512, which results in faster transfers. You can set a packet size of up to 2,048 bytes.
  • The SuperKermit file transfer protocol is a sliding-window, or full-duplex protocol, which means that it sends data continuously while receiving occasional acknowledgments from the host.

In Reflection, you can set the number of packets that one side can receive before sending an acknowledgment. This value is 0-based, which means that the default setting of 1 (one) configures Reflection for a two-packet sliding-window under Kermit.

Xmodem

Xmodem is a public domain program used for file transfers, and is available for a variety of computers. The Xmodem binary transfer protocol transfers data in 128-byte data blocks. Reflection can receive a file in either 128-byte or 1K blocks, depending on the configuration of the remote system.

Most versions of Xmodem can perform CRC (cyclic redundancy check) error checking, which is accomplished when, from the Transfer Settings dialog box Xmodem tab, Xmodem-CRC is selected as the extension. This causes a 2-byte CRC and sets the packet size to 128-byte packets (not including overhead). The other two extension options are:

Xmodem

1-byte checksum, 128-byte packets

Xmodem-1K

2-byte CRC, 1024-byte packets

With the default Extensions option selected (Xmodem-CRC), on receives, Reflection automatically switches between Xmodem-CRC and Xmodem-1K, to match what the other end is sending.

Related Topics

Transfer a File

Configure File Transfer

Reflection FTP Client