File Based Terminal Messaging

Neither platform has an inter-process signalling primitive, so anything wanting to pass a signal between two EAs - or between EAs running in different terminal instances - has to go through the file system. The obvious design is one shared file per channel that senders append to and readers poll, but neither platform gives a safe way to do that concurrently: there is no share-mode flag that lets two writers interleave an append safely, and a reader can catch the file mid-write and see a truncated or duplicated line. This header avoids the problem instead of trying to solve it: every message is its own uniquely named file. Sending is a single create-write-close that never opens anything another program might be touching. Receiving lists the channel's folder, reads each file found, and deletes it once delivered - a single-file read-then-delete per message rather than a shared read-modify- write. Both operations are things the file system already makes atomic on their own, so there is no lock file, no retry loop and no window where a reader can observe a half-written message. Filenames encode GetTickCount() and a monotonic per-process counter, so FileMsgReceiveAll() delivers messages in the order they were sent simply by sorting filenames alphabetically - no separate sequence file to maintain. Messages can go through the private per-terminal sandbox or the shared common Files folder (FILE_COMMON) that every terminal on the machine can see, which is what makes cross-terminal signalling possible at all. Notes and limitations - Delivery order relies on GetTickCount(), which wraps after roughly 49 days of continuous uptime on both platforms; the per-process counter appended to every filename still guarantees uniqueness across that wrap, only the strict chronological ordering guarantee weakens right at the wrap boundary. - This is at-most-once delivery with no acknowledgement and no retry: if a receiver crashes after FileMsgReceiveAll() reads a message but before it acts on it, that message is already deleted and gone. Use deleteAfterRead=false plus your own acknowledgement scheme if a message must survive a receiver crash. - No message size limit is enforced; very large payloads work but are read entirely into memory as one string. - FILE_COMMON messages are visible to every terminal on the machine that shares the same common Files folder - do not use a common-folder channel name generic enough that an unrelated EA on the same PC might collide with it (e.g. prefix with your strategy's name, as the demo does).

Script · MT4 · v1.0 · Free

Tags: Channels & Envelopes · Buy/Sell Arrows · MT4 Script · MQL4 Source Code

MQL4 & MQL5 scripts · PolyMaria