Toolbox connection problem

Another "baby step" into the Toolbox:
We've taken some code I wrote on one AS/400, running locally and accessing
files (2 files of identical format) locally through Toolbox calls, and
incorporated it into a program that runs on a Windoze box, and accesses a
different AS/400 through a network connection. It gets as far as
instantiating a SequentialFile, and getting an AS400FileRecordDescription
on a file (I haven't yet inserted a diagnostic to determine whether the
record description comes back valid), but then it starts throwing
exceptions, trying to do a retrieveRecordFormat() on the record
dscription, and it fails to open the files.

The files are there. In the library where they're expected to be.

The initial exception appears to be a "Connection Refused" at the
retrieveRecordFormat.

WRKTCPSTS shows that the "as-signon" and "as-svrmap" servers on the target
box have been recently accessed, but not the as-cent, as-data, as-dtaq,
as-file, as-netprt, as-rmtcmd, as-netd, as-tran, or as-vrtp.

About all the code I can share is:
. . .
System.out.println("$$$ Filename = " + fileName.getPath());
SequentialFile file = new SequentialFile(as400, fileName.getPath());
. . .
System.out.println("$$$ Archive = " + archName.getPath());
SequentialFile arch = new SequentialFile(as400, archName.getPath());
AS400FileRecordDescription recDes = new AS400FileRecordDescription(as400,
fileName.getPath());
try {
    RecordFormat recFmt = recDes.retrieveRecordFormat()[0];
    System.out.println("$$$ Format = " + recFmt.getName());
    file.setRecordFormat(recFmt);
    arch.setRecordFormat(recFmt);
    file.open(SequentialFile.READ_WRITE, 1,
SequentialFile.COMMIT_LOCK_LEVEL_NONE);
    arch.open(SequentialFile.WRITE_ONLY, 1,
SequentialFile.COMMIT_LOCK_LEVEL_NONE);
    System.out.println("event file is open:" + file.isOpen());
    System.out.println("event archive file is open:" + arch.isOpen());
. . .

Anybody know what could be going wrong?

--
JHHL