Added support for timeout when opening a TCPSocket

See njh#163

Author: ccutrer

README.md

@@ -82,6 +82,15 @@ client.ca_file   = path_to('root-ca.pem')
 client.connect
 ~~~
 
+The default timeout when opening a TCP Socket is 30 seconds. To specify it explicitly, use 'connect_timeout =>':
+
+~~~ ruby
+client = MQTT::Client.connect(
+  :host => 'myserver.example.com',
+  :connect_timeout => 15
+)
+~~~
+
 The connection can either be made without the use of a block:
 
 ~~~ ruby

lib/mqtt/client.rb

@@ -41,6 +41,9 @@ class Client
     # Number of seconds to wait for acknowledgement packets (default is 5 seconds)
     attr_accessor :ack_timeout
 
+    # Number of seconds to connect to the server (default is 90 seconds)
+    attr_accessor :connect_timeout
+
     # How many times to attempt re-sending packets that weren't acknowledged
     # (default is 5) before giving up
     attr_accessor :resend_limit
@@ -84,6 +87,7 @@ class Client
       clean_session: true,
       client_id: nil,
       ack_timeout: 5,
+      connect_timeout: 30,
       resend_limit: 5,
       reconnect_limit: 5,
       reconnect_backoff: 2,
@@ -496,7 +500,7 @@ def clear_queue
 
     def connect_internal
       # Create network socket
-      tcp_socket = TCPSocket.new(@host, @port)
+      tcp_socket = open_tcp_socket
 
       if @ssl
         # Set the protocol version
@@ -793,5 +797,17 @@ def next_packet_id
       @last_packet_id = 1 if @last_packet_id > 0xffff
       @last_packet_id
     end
+
+    def open_tcp_socket
+      return TCPSocket.new @host, @port, connect_timeout: @connect_timeout if RUBY_VERSION.to_f >= 3.0
+
+      begin
+        Timeout.timeout(@connect_timeout) do
+          return TCPSocket.new(@host, @port)
+        end
+      rescue Timeout::Error
+        raise IO::TimeoutError, "Connection timed out for \"#{@host}\" port #{@port}"
+      end
+    end
   end
 end

spec/mqtt/client_spec.rb

@@ -626,6 +626,11 @@ def register_for_ack(packet)
       end
     end
 
+    it "respects connect_timeout" do
+      client = MQTT::Client.new(host: "198.51.100.1", connect_timeout: 0.1)
+      expect { client.connect }.to raise_error(IO::TimeoutError)
+    end
+
     it "respects timeouts" do
       require "socket"
       rd, _wr = UNIXSocket.pair