write_nonblock

Writes str in the non-blocking manner.

If there are buffered data, it is flushed at first. This may block.

write_nonblock returns number of bytes written to the SSL connection.

When no data can be written without blocking, It raises OpenSSL::SSL::SSLError extended by IO::WaitReadable or IO::WaitWritable.

IO::WaitReadable means SSL needs to read internally. So write_nonblock should be called again after underlying IO is readable.

IO::WaitWritable means SSL needs to write internally. So write_nonblock should be called again after underlying IO is writable.

So OpenSSL::Buffering#write_nonblock needs two rescue clause as follows.

# emulates blocking write. begin

result = ssl.write_nonblock(str)

rescue IO::WaitReadable

IO.select([io])
retry

rescue IO::WaitWritable

IO.select(nil, [io])
retry

end

Note that one reason that write_nonblock read from a underlying IO is the peer requests a new TLS/SSL handshake. See openssl FAQ for more details. http://www.openssl.org/support/faq.html

# File ext/openssl/lib/openssl/buffering.rb, line 290
  def write_nonblock(s)
    flush
    syswrite_nonblock(s)
  end