WM_COPYDATA SendMessage - Can it send big strings?

Question

I will have to implement a WM_COPYDATA IPC between 2 applications. I have seem samples on internet, but all of them only send strings that are less than 255 characters.

I want to send a big string (more than 1k) to another process using WM_COPYDATA. Is it possible? What are the limitations? Should I send a stream instead of a string or record?

Both applications were developed by me using Delphi 2010.

I don't know. I gave you +1 to balance it. There are sometimes random down voters on SO, especially here in [tag:delphi]. The same thing happened to [a question of mine](http://stackoverflow.com/questions/9572887/3d-library-recommendations-for-interactive-spatial-data-visualisation) a couple of days ago. — David, Mar 07 '12 at 14:00

score 8 · Accepted Answer · answered Mar 07 '12 at 13:00

8

There are no limitations. You can send data as large as you like, subject to available memory constraints, using WM_COPYDATA.

answered Mar 07 '12 at 13:00

David Heffernan

601,492
42
1,072
1,490

So basically 2 gigs or so on win32? :-) – Warren P Mar 07 '12 at 18:37
@Warren Hard to find that much contiguous address space in a 32 bit process. – David Heffernan Mar 07 '12 at 18:43
2

If you really need to send 2GB of data, you are better off just using a temp file and passing the filename, or use COM's `IDataObject` and `IStream` interfaces instead. – Remy Lebeau Mar 07 '12 at 19:06

WM_COPYDATA SendMessage - Can it send big strings?

1 Answers1