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Asked: 2026-05-22T03:13:14+00:00

Using the recv() function in C to read from a ‘stream’ socket, can the

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Using the recv() function in C to read from a ‘stream’ socket, can the len parameter be zero?

The recv() function returns zero for ‘remote connection closed’ and the number of bytes actually read on normal operation, so it sounds problematic if it should read zero bytes.

P.S.
Yes I know to deal with it separately, and not get to this situation, still I’m wondering if the function can handle it, I can’t find any documentation about it.

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1 Answer

  1. Editorial Team

    I believe the answer is “it depends”. If it is not specified by the standard (and indeed I believe it isn’t) any implementation could do as it pleases.

    • It could fail with EINVAL
    • It could hang
    • It could return 0 and go on
    • It could print a funny message and start the game rogue (I understand gcc used to do that :)) )

    Actually on my implementation, it returns 0 and goes on. To check if it failed or simply returned 0, you can check errno after the call, so it’s not as problematic as you may think.

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