One simulator. Any ISO 8583 interface.

Any ISO 8583 interface

Nothing is hardcoded to one network. Point FlexSim at a switch, an issuer host, an acquirer front end or a test harness, and describe what that link expects.

Any scheme, edited not compiled

Build the message format in the app: fields, lengths, encodings, bitmap format, application headers and nested subfields. Switch between specifications without restarting, and rename one without orphaning a thing.

Acquirer and issuer modes

Answer requests as the issuer host, or send them as the acquirer. The same test case definitions serve both directions — it is a setting on the case, not a separate tool.

A rule set per test case

Say what a correct reply looks like — per field, per case — and let the run decide pass or fail instead of you reading hex. Checking can be switched off per case without losing the rules.

Save a card once, use it everywhere

PAN, expiry, service code, PIN, sequence number, track 2 layout and every verification value live on the card. Any test case can reach them, so a card change lands in all of them at once.

Auto-calculated from your keys

Store the keys once and let FlexSim work out the values that depend on them — verification values, PIN blocks, message authentication codes and chip cryptograms — instead of pasting figures from somewhere else.

Server or client, your header length

Dial out as a client or accept connections as a server, with the length header the link actually uses rather than the one a tool assumed.

Every message, parsed on screen

Requests and responses shown as named fields, not a wall of hex — with the raw bytes still there when you need them. Colour-coded and readable at a glance.

Go back through every run

Past exchanges are kept and searchable long after the session that produced them, so a question about last week's test has an answer.

Run a case as many times as you need

Set a count beside Send and the case repeats — for volume, for soak testing, or just to watch a sequence advance. Stop halts it immediately.

• Generated fields are recomputed each pass, so it is many messages, not one message many times
• Trace numbers and counters carry on where they left off
• In acquirer mode the same count is how many requests to answer

Group cases and run the tree

Cases live in suites per specification. Run one, run the lot, and get a pass or fail per case rather than a log to read line by line.

• Results stream in as each case finishes
• Export a spreadsheet or a self-contained report
• Failures keep their raw bytes for investigation

Start from a captured message

Paste a hex dump and FlexSim parses it against the active specification, turning it into a test case with the fields already filled in — structure taken apart the same way it was put together.

Take the transaction back

A case can follow its own request with the reversal for it, once the reply has landed. Most of the message is echoed from what was actually sent; the few fields that differ you type in.

• 0200 reverses as 0400 on its own, or set the message type yourself
• A delay before it goes, so the host sees the gap a timed-out terminal leaves
• In an iteration run, one reversal per pass

Four profiles, ready to use

The app arrives with four working message formats already built, so there is something to send on the first run. Open any of them in the editor and bend it to the document you were actually given.

Any card value, in any field

Point a data element at the card value it should carry — PAN, track, PIN block, any verification value, even a key — instead of being limited to whatever its field number happened to imply.

Say what a good reply looks like

Rules are attached to the case, so the same message sent in two contexts can be judged by two different standards.

Checking switches off without loss

Turn validation off for a case and it still runs and still sends — the reply simply is not judged, and the rules are waiting when you turn it back on.

Results you can send on

Suite results stream in as each case finishes and export as a spreadsheet or a self-contained report, with the raw bytes kept for anything that failed.

Export suites, keep the secrets

Suites round-trip through JSON and XML so a colleague can import yours. Card and key material is deliberately left out of the file.

A scratchpad, built in

Work out a CVV, iCVV, PVV or PIN block from a PAN and a key with no card saved, convert between ASCII, EBCDIC and hex, decode a tag-length-value blob, combine or wrap keys — without a second window on another screen.

A master password, if you want one

Card and key material is encrypted at rest. Set a master password and the database is re-encrypted under it, with the app locked until it is entered.

One file holds your work

Specifications, suites, cards, keys, settings and history live in a single database file. Copy it to another machine and carry on where you stopped.