Use the open_timeout kwarg where available

Author: mohamedhafez

lib/net/smtp.rb

@@ -263,6 +263,7 @@ def initialize(address, port = nil, tls: false, starttls: :auto, tls_verify: tru
       @tls_verify = tls_verify
       @tls_hostname = tls_hostname
       @ssl_context_params = ssl_context_params
+      @tcp_socket_supports_open_timeout = nil
     end
 
     # If +true+, verify th server's certificate.
@@ -659,17 +660,43 @@ def finish
 
     private
 
-    def tcp_socket(address, port)
-      TCPSocket.open address, port
+    def tcp_socket(address, port, open_timeout: nil)
+      if open_timeout
+        TCPSocket.open(address, port, nil, nil, open_timeout: open_timeout)
+      else
+        TCPSocket.open(address, port)
+      end
     end
 
     def do_start(helo_domain, user, secret, authtype)
       raise IOError, 'SMTP session already started' if @started
       if user || secret || authtype
         check_auth_args authtype, user, secret
       end
-      s = Timeout.timeout(@open_timeout, Net::OpenTimeout) do
-        tcp_socket(@address, @port)
+      begin
+        s =
+          case @tcp_socket_supports_open_timeout
+          when nil, true
+            begin
+              sock = tcp_socket(@address, @port, open_timeout: @open_timeout)
+              @tcp_socket_supports_open_timeout = true
+              sock
+            rescue ArgumentError => e
+              raise unless e.message.include?('unknown keyword: :open_timeout') || e.message.include?('wrong number of arguments (given 5, expected 2..4)')
+              @tcp_socket_supports_open_timeout = false
+
+              Timeout.timeout(@open_timeout, Net::OpenTimeout) do
+                tcp_socket(@address, @port)
+              end
+            end
+          when false
+            Timeout.timeout(@open_timeout, Net::OpenTimeout) do
+              tcp_socket(@address, @port)
+            end
+          end
+      rescue => e
+        e = Net::OpenTimeout.new(e) if e.is_a?(Errno::ETIMEDOUT) # for compatibility with previous versions
+        raise e
       end
       logging "Connection opened: #{@address}:#{@port}"
       @socket = new_internet_message_io(tls? ? tlsconnect(s, @ssl_context_tls) : s)