Hello Perl experts. I'm writing a Perl client/server program that operates over a remote shell (SSH) with a simple line-based text protocol. However, I need to also transmit blobs of binary data.

The client uses open2(*Reader, *Writer, "ssh ... my_server") to get a Reader and a Writer filehandle to the remote server.

The server simply reads <STDIN> and writes to <STDOUT>

This setup works fine for the text-based parts of the protocol.

I am not sure of the best way to do the binary transfer from client to server. I tried using syswrite() from the client and sysread() on the server (basically) as like this:

Client: Sends text "----- Chunk of length $len -----\n" Server: Receives above line OK. Parses correctly and calls sysread(STDIN, $buf, $len);

Client: Sends exactly $len bytes with syswrite(Writer, $data, $len)

Server: sysread() blocks indefinitely

If I send an extra "\n" after my chunk of data, sysread() unblocks, but I am concerned that if my binary data contains newlines that this may cause other problems.

I realise it is ill-advised to mix sysread()/syswrite() with other (buffered) IO types, and that this is part of the problem. Any suggestions on either how to make this work, or a better design?

Thank you!

In reply to Mixing sysread() with <FILEHANDLE>? by wanna_code_perl

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