Add Modbus over TCP

[elnappo]

At the moment, I don't have a strong rule for this.
Protocol specification: http://www.modbus.org/docs/Modbus_Application_Protocol_V1_1b3.pdf
Port: 502

127.0.0.1 127.0.0.1 502 29956 6 1227729974.566 11 11 00000000 .... 11 00000000 .... 11
127.0.0.1 127.0.0.1 502 58242 6 1227729975.138 10 12 00000000 .... 10 00000000 .... 12
127.0.0.1 127.0.0.1 502 6806 6 1227729974.108 11 12 00000000 .... 11 00000000 .... 12
127.0.0.1 127.0.0.1 502 4308 6 1227729973.959 11 19 00000000 .... 11 00000000 .... 19
172.17.203.47 172.17.203.34 502 3201 6 1284636111.131 198 108 00000000 .... 22 00000000 .... 12
192.168.2.25 192.168.2.100 502 1164 6 1267616448.089 0 12 00000000 .... 0 00000000 .... 12
192.168.2.25 192.168.2.100 502 1165 6 1267616448.172 0 12 00000000 .... 0 00000000 .... 12
192.168.2.25 192.168.2.100 502 1166 6 1267616448.705 40 48 00000000 .... 10 00000000 .... 12
192.168.45.205 192.168.45.20 502 1083 6 1218760999.307 78 56 00010000 .... 16 00010000 .... 14
10.0.0.8 10.0.0.57 502 2579 6 1093521953.490 0 24 00000000 .... 0 00010000 .... 12
10.0.0.3 10.0.0.57 502 2578 6 1093521681.697 138 112 00000000 .... 9 00000000 .... 12
10.0.0.3 10.0.0.9 502 3082 6 1093522326.102 69 72 00010000 .... 10 00010000 .... 12
10.0.0.8 10.0.0.57 502 2585 6 1093522946.554 0 926 00000000 .... 0 00010000 .... 451
10.0.0.57 10.0.0.8 4446 502 6 1093523065.562 128 0 00010000 .... 10 00000000 .... 0
166.161.16.230 192.168.66.235 502 2582 6 1153491879.610 1278 1692 00000000 .... 9 00000000 .... 12