Socket: Client was disconnected or not?

Question

I am creating socket server. But I do not know, How I can know client disconnected or not? I am creating server under Windows and using berkeley sockets function (read, send, connect....). Preferably I want a cross-platfomennoe solution (without WSA functions).

I can write to socket 0 byte and ckeck error. But it is not good solution.

Answer 1

When a client disconnects, you'll get a "read" event but the read() will return 0.

ssize_t bytes_read;
if ((bytes_read = read(...)) == 0)
{
    // client disconnected
}
else if (bytes_read == -1)
{
    // some sort of error (also no data available when using non-blocking sockets).
}
else
{
    // you have bytes_reads bytes to process
}