Port TCP UDP Description Status 0 UDP Reserved Official 0 TCP Programming technique for specifying system-allocated (dynamic) ports[2] Unofficial 1 TCP UDP TCP Port Service Multiplexer (TCPMUX) Official 2 TCP UDP CompressNET[3] Management Utility[4] Official 3 TCP UDP CompressNET[3] Compression Process[5] Official 4 TCP UDP Unassigned Official 5 TCP UDP Remote Job Entry Official 7 TCP UDP Echo Protocol Official 8 TCP UDP Unassigned Official 9 UDP Wake-on-LAN Unofficial 9 TCP UDP Discard Protocol Official 10 TCP UDP Unassigned Official 11 TCP UDP Active Users (systat service)[6][7] Official 12 TCP UDP Unassigned Official 13 TCP UDP Daytime Protocol (RFC 867) Official 14 TCP UDP Unassigned Official 15 TCP UDP Previously netstat service[6] Unofficial 16 TCP UDP Unassigned Official 17 TCP UDP Quote of the Day Official 18 TCP UDP Message Send Protocol Official 19 TCP UDP Character Generator Protocol (CHARGEN) Official 20 TCP UDP FTP data transfer Official 21 TCP FTP