Replace Timeout.timeout with socket timeout

Timeout.timeout is inefficient since it spins up a new thread for each invocation, use Socket.tcp's connect_timeout option instead when we aren't using SOCKS (we can't replace Timeout.timeout for SOCKS yet since SOCKSSocket doesn't have a connect_timeout option).

Author: mohamedhafez

lib/net/ftp.rb

@@ -330,14 +330,19 @@ def return_code=(s) # :nodoc:
  # SOCKS_SERVER, then a SOCKSSocket is returned, else a Socket is
  # returned.
  def open_socket(host, port) # :nodoc:
- return Timeout.timeout(@open_timeout, OpenTimeout) {
- if defined? SOCKSSocket and ENV["SOCKS_SERVER"]
-  @passive = true
+ if defined? SOCKSSocket and ENV["SOCKS_SERVER"]
+ @passive = true
+ Timeout.timeout(@open_timeout, OpenTimeout) do
  SOCKSSocket.open(host, port)
- else
- Socket.tcp(host, port)
  end
- }
+ else
+ begin
+ Socket.tcp host, port, nil, nil, connect_timeout: @open_timeout
+ rescue Errno::ETIMEDOUT #raise Net:OpenTimeout instead for compatibility with previous versions
+ raise Net::OpenTimeout, "Timeout to open TCP connection to "\
+ "#{host}:#{port} (exceeds #{@open_timeout} seconds)"
+ end
+ end
  end
  private :open_socket