XYModem is a Java implementation of the XModem and YModem file download protocols. It supports:
- XModem-Checksum
- XModem-CRC
- XModem-1K
- YModem-Batch
- YModem-G
It also implements just enough of ZModem for AutoDownload support, though that only works if the sending ZModem implemenation provides automatic fallback to XModem or YModem.
<dependency>
<groupId>net.digger</groupId>
<artifactId>xymodem</artifactId>
<version>1.1.0</version>
</dependency>
Create an implemenation of IOHandler, to provide I/O methods appropriate for your environment.
Create a new instance of XYModem, giving it an instance of your IOHandler implementation.
XYModem xymodem = new XYModem(ioHandler);
After the sender has been instructed to begin an XModem or YModem download, pass control to XYModem.
xymodem.download();
XYModem will handle the handshaking and download process, using
IOHandler.read(timeout) to read bytes from the sender and
IOHandler.write(ch) to write bytes to the sender.
Each time a file download is complete, it will call
IOHandler.received(download) to pass details of the downloaded
file. This may be called more than once for a batch download
(YModem-Batch or YModem-G).
When the download session is complete, XYModem.download() will return.
During the download process, IOHandler.log(message) and IOHandler.progress(bytes, total)
will be called with messages and download progress.
Before beginning a download, you can call xymodem.setOverrunOption()
to set the desired behavior if a file received via the YModem protocol
exceeds the size claimed by the sender.
AutoDownload
Before a download has been initiated, incoming bytes can be checked for a ZModem download signature.
xymodem.autoDownloadDetect(ch);
This method will return true if a ZModem ZRQINIT header is detected,
indicating the sender is ready to begin download. It can be used to
automatically initiate a download:
if (xymodem.autoDownloadDetect(ch)) {
xymodem.download();
}
Please note: If the sending ZModem implementation does not support
automatic fallback to XModem or YModem, the handshaking will time
out and download() will return, with the sender still waiting
for a ZModem download to begin.
XYModem is provided under the terms of the GNU LGPLv3.