Modified the clearing buffer to @pwood variant.

examples/perfomance_rtu_via_tcp.rb

@@ -0,0 +1,55 @@
+$:.unshift File.join(File.dirname(__FILE__),'../lib')
+
+require 'rmodbus'
+require 'benchmark'
+
+include ModBus
+
+TIMES = 1000
+
+srv = ModBus::RTUViaTCPServer.new 1502 
+srv.coils = [0,1]  * 50
+srv.discrete_inputs = [1,0]  * 50
+srv.holding_registers = [0,1,2,3,4,5,6,7,8,9]  * 10
+srv.input_registers = [0,1,2,3,4,5,6,7,8,9]  * 10
+srv.start
+
+
+cl = RTUViaTCPClient.new('127.0.0.1', 1502)
+cl.with_slave(1) do |slave|
+  Benchmark.bmbm do |x|
+    x.report('Read coils') do
+      TIMES.times { slave.read_coils 0, 100 }
+    end
+
+    x.report('Read discrete inputs') do
+      TIMES.times { slave.read_discrete_inputs 0, 100 }
+    end
+
+    x.report('Read holding registers') do
+      TIMES.times { slave.read_holding_registers 0, 100 } 
+    end
+
+    x.report('Read input registers') do
+      TIMES.times { slave.read_input_registers 0, 100 }
+    end
+
+    x.report('Write single coil') do
+      TIMES.times { slave.write_single_coil 0, 1 }
+    end
+
+    x.report('Write single register') do
+      TIMES.times { slave.write_single_register 100, 0xAAAA }
+    end
+
+    x.report('Write multiple coils') do
+      TIMES.times { slave.write_multiple_coils 0, [1,0] * 50 }
+    end    
+
+    x.report('Write multiple registers') do
+      TIMES.times { slave.write_multiple_registers 0, [0,1,2,3,4,5,6,7,8,9] * 10  }
+    end
+  end
+end
+cl.close
+srv.stop

lib/rmodbus/rtu.rb

@@ -23,7 +23,6 @@ def read_rtu_response(io)
       msg = nil
       while msg.nil?
 	      msg = io.read(2)
-        sleep(0.01)
       end
 
       function_code = msg.getbyte(1)
@@ -46,11 +45,14 @@ def read_rtu_response(io)
     end
 
     def clean_input_buff
-      rt = @io.read_timeout
-      @io.read_timeout = -1
-      @io.read # Clean input buffer
-
-      @io.read_timeout = rt
+      begin
+        # Read up to 1500 bytes of trash.
+        @io.read_nonblock(1500)
+      rescue Errno::EAGAIN
+        # Ignore the fact we couldn't read.
+      rescue Exception => e
+        raise e
+      end
     end
 
     def send_rtu_pdu(pdu)
@@ -119,7 +121,6 @@ def serv_rtu_requests(io, &blk)
           log "Server TX (#{resp.size} bytes): #{logging_bytes(resp)}"
           io.write resp
 		    end
-        sleep(0.01)
 	    end
     end
 

lib/rmodbus/tcp_server.rb

@@ -57,7 +57,6 @@ def serve(io)
           log "Server TX (#{resp.size} bytes): #{logging_bytes(resp)}"
           io.write resp
         end
-        sleep(0.01)
 			end
 		end
 	end

rmodbus.gemspec

@@ -23,4 +23,5 @@ Gem::Specification.new do |gem|
   gem.add_development_dependency 'pry'
   gem.add_development_dependency 'serialport' unless RUBY_PLATFORM == 'java'
   gem.add_development_dependency 'guard-rspec'
+  gem.add_development_dependency 'ruby-prof'
 end

spec/logging_spec.rb

@@ -42,8 +42,8 @@ def mock_query(request, response)
       @sp = mock('Serial port')
       SerialPort.should_receive(:new).with("/dev/port1", 9600, 7, 2, SerialPort::ODD).and_return(@sp)    
 
-      @sp.stub!(:read_timeout=)
       @sp.stub!(:read_timeout)
+      @sp.stub!(:read_timeout=)
 
       @slave = ModBus::RTUClient.new("/dev/port1", 9600, :data_bits => 7, :stop_bits => 2, :parity => SerialPort::ODD).with_slave(1)
       @slave.read_retries = 0
@@ -52,7 +52,7 @@ def mock_query(request, response)
     it 'should log rec\send bytes' do
       request = "\x3\x0\x1\x0\x1"
       @sp.should_receive(:write).with("\1#{request}\xd5\xca")
-      @sp.should_receive(:read).and_return("\xff\xff") # Clean a garbage
+      @sp.should_receive(:read_nonblock).and_return("\xff\xff") # Clean a garbage
       @sp.should_receive(:read).with(2).and_return("\x1\x3")
       @sp.should_receive(:read).with(1).and_return("\x2")
       @sp.should_receive(:read).with(4).and_return("\xff\xff\xb9\xf4")

spec/rtu_client_spec.rb

@@ -6,7 +6,7 @@
     SerialPort.should_receive(:new).with("/dev/port1", 9600, 8, 1, 0).and_return(@sp)    
     @sp.stub!(:read_timeout=)
     @sp.stub!(:read_timeout)
-    @sp.stub!(:read)
+    @sp.stub!(:read_nonblock)
 
     @cl = ModBus::RTUClient.new("/dev/port1", 9600, :data_bits => 8, :stop_bits => 1, :parity => SerialPort::NONE)
     @slave = @cl.with_slave(1)

spec/rtu_via_tcp_client_spec.rb

@@ -6,8 +6,7 @@
       @sock = mock('Socked')
       TCPSocket.should_receive(:new).with("127.0.0.1", 10002).and_return(@sock)    
       @sock.stub!(:read_timeout=)
-      @sock.stub!(:read_timeout)
-      @sock.stub!(:read)
+      @sock.stub!(:read_nonblock)
 
       @cl = ModBus::RTUViaTCPClient.new("127.0.0.1")
       @slave = @cl.with_slave(1)