Communication Control System, Image Processing Unit, Router, Communication Relay Device and Non-Transitory Recording Medium

Abstract

A communication control system comprises: a router that connects a first network and a second network; a communication relay device that connects the first network and the second network; and a hardware processor that: determines whether a first packet received from the first network is a packet to be discarded by the router, transmits a second packet corresponding to the first packet to the second network when the first packet is determined as the packet to be discarded by the router, and rewrites a transmitter IP address of a response packet corresponding to the second packet to an IP address of the router and sends the response packet to the first network when the response packet is received from the second network.

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         9 . A router that connects a first network and a second network, comprising a hardware processor that:
 sends a predetermined packet to said second network when the predetermined packet to be sent to said second network is received from said first network, and discards a packet when the packet different from the predetermined packet is received from said first network;
 obtains a packet to be sent to said first network from a communication relay device which is connected between said first network and said second network prior to the transmission to said first network; and 
 rewrites a transmitter IP address of the packet to an IP address of said router and sends to said first network when the packet sent from said communication relay device is obtained. 
   
     
     
         10 . The router according to  claim 9 , wherein
 an image forming device capable of producing printed outputs is connected to said second network,   said hardware processor discards the packet to retrieve said image forming device when the packet is received from said first network,   obtains a response packet when the response packet corresponding to the packet to retrieve said image forming device is sent to said first network from said communication relay device, and   rewrites the transmitter IP address of the response packet.   
     
     
         11 . The router according to  claim 9 , wherein
 said hardware processor forwards a unicast packet specifying a specific port number to the IP address of said second network corresponding to the specific port number when the unicast packet is received from said first network.   
     
     
         12 . A communication relay device connected in parallel with a router connecting a first network and a second network, comprising a hardware processor that:
 determines whether a first packet received from said first network is a packet to be discarded by said router;   transmits a second packet corresponding to said first packet to said second network when said first packet is determined to be the packet discarded by said router; and   rewrites a transmitter IP address of a response packet corresponding to said second packet to an IP address of said router and sends the response packet to said first network when the response packet is received from said second network.   
     
     
         13 . The communication relay device according to  claim 12 , wherein
 said hardware processor determines said first packet as the packet to be discarded by said router when said first packet is a broadcast packet or a multicast packet.   
     
     
         14 . The communication relay device according to  claim 12 , wherein
 an image forming device capable of producing printed outputs is connected to said second network, and   said hardware processor determines said first packet as the packet to be discarded by said router when said first packet is the packet to retrieve said image forming device.   
     
     
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         21 . A non-transitory recording medium storing a computer readable program to be executed by a computer of a router connecting a first network and a second network, execution of the computer readable program by said computer of said router causing said computer of said router to perform:
 sending a predetermined packet to said second network when the predetermined packet to be sent to said second network is received from said first network, and discarding a packet when the packet different from the predetermined packet is received from said first network;   obtaining a packet to be sent to said first network from a communication relay device which is connected between said first network and said second network prior to the transmission to said first network; and   rewriting a transmitter IP address of the packet to an IP address of said router and sending to said first network when the packet sent from said communication relay device is obtained.   
     
     
         22 . The non-transitory recording medium according to  claim 21 , wherein
 an image forming device capable of producing printed outputs is connected to said second network, and
 the computer readable program causes the computer of said router to perform: 
 discarding the packet to retrieve said image forming device when the packet is received from said first network; 
   obtaining a response packet when the response packet corresponding to the packet to retrieve said image forming device is sent to said first network from said communication relay device; and   rewriting the transmitter IP address of the response packet.   
     
     
         23 . The non-transitory recording medium to  claim 21 , wherein the computer readable program causes the computer of said router to perform:
 forwarding a unicast packet specifying a specific port number to the IP address of said second network corresponding to the specific port number when the unicast packet is received from said first network.   
     
     
         24 . A non-transitory recording medium storing a computer readable program to be executed by a computer of a communication relay device connected in parallel with a router connecting a first network and a second network, wherein execution of the computer readable program by said computer of said communication relay device causing said computer of said communication relay device to perform:
 determining whether a first packet received from said first network is a packet to be discarded by said router;   transmitting a second packet corresponding said first packet to said second network when said first packet is determined to be the packet discarded by said router; and   rewriting a transmitter IP address of a response packet corresponding to said second packet to an IP address of said router and sending the response packet to said first network when the response packet is received from said second network.   
     
     
         25 . The non-transitory recording medium according to  claim 24 , wherein the computer readable program causes the computer of said communication relay device to perform:
 determining said first packet as the packet to be discarded by said router when said first packet is a broadcast packet or a multicast packet.   
     
     
         26 . The non-transitory recording medium according to  claim 24 , wherein
 an image forming device capable of producing printed outputs is connected to said second network, and   the computer readable program causes the computer of said communication relay device to perform:   determining said first packet as the packet to be discarded by said router when said first packet is the packet to retrieve said image forming device.