Abstract:
A game device regularly transmits communication status information to communication partners thereof, the communication status information indicating whether or not communication between the game device and each of the communication partners is possible. If, when the game device receives from each of the communication partners the communication status information about said each of the communication partners, the communication status information about any of the communication partners indicates a particular game device as being unable to perform communication, the game device updates the communication status information about the game device such that the communication status information about the game device indicates the particular game device as being unable to perform communication. When the communication status information about all of the communication partners indicate a particular game device as being unable to perform communication, the game device ceases communicating with the game device. This makes it possible to disconnect from a network a game device whose connection status to the other user terminals in the network is unstable or which is in a state of connection-disabled, thereby preventing a status of a game commonly executed by user terminals in the game system from being differently displayed on a screen of each of the user terminals.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     The disclosure of Japanese Patent Application No. 2005-328149 is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a storage medium storing a game program and a game device, and particularly to a storage medium storing a game program and a game device which are used for a game system in which a plurality of game devices transmit and receive game data to and from each other, and each game device performs game processes by using the game data received from the other game devices.  
         [0004]     1. Description of the Background Art  
         [0005]     Network game systems can be roughly categorized into two types, i.e., client/server type network game systems and peer-to-peer network game systems.  
         [0006]     In a client/server type network game system, each user terminal is connected to a game server as a client, and the game server mainly performs game processes to execute a game. In the client/server type network game system, the greater the number of user terminals connected to the game server, the greater is the processing load on the game server. For this reason, the game server is required to have high capacity. This leads to a high cost of constructing the network game system, which is a disadvantage of the client/server type.  
         [0007]     On the other hand, in a peer-to-peer network game system, basically, a game is executed through communications performed among user terminals. For this reason, a game server having high capacity, which is necessary for the client/server type network game system, is not necessary. In addition, data transfer among the user terminals is not required to be performed via a game server. Therefore, the peer-to-peer network game system is suitable for executing a game requiring real-time processing such as a racing game. An exemplary peer-to-peer network game system is disclosed in a non-patent document 1 (Jung Wun-Chul, “Online Game Programming”, SOFTBANK Publishing Inc., Mar. 3, 2005, first edition, pp. 218-222).  
         [0008]     Although the above non-patent document 1 discloses a manner of connecting a user terminal to the peer-to-peer network, the non-patent document 1 does not disclose a manner of disconnecting from the network a user terminal whose connection status to the other user terminals in the network is unstable or which is in a state of connection-disabled.  
         [0009]     Unlike the client/server type network game system, the peer-to-peer network game system has a feature in which user terminals each individually perform arithmetic processing in accordance with signals received from the other user terminals. For this reason, if, in the game system, each user terminal freely ceases communicating with a user terminal whose connection status to said each user terminal is unstable or which has been unable to communicate with said each user terminal for a predetermined period of time, a status of a game commonly executed by the user terminals is differently displayed on a screen of each of the user terminals. This may cause a significantly negative effect on a progress of the game.  
         [0010]     For example, if, in a peer-to-peer network game system comprising four game devices A to D as shown in  FIG. 27 , a failure occurs on a communication line between the game devices A and B, the game device A continues to perform game processes in accordance with game data of the game device A and game data transmitted from the game devices C and D, since the game device A cannot receive game data from the game device B. In such a case, however, the game device C continues to perform game processes in accordance with game data of the game device C and game data transmitted from the game devices A, B and D. This consequently causes a difference between a result of the game processes performed by the game device A and a result of the game processes performed by the game device C.  
       SUMMARY OF THE INVENTION  
       [0011]     Therefore, an object of the present invention is to provide a network game system capable of disconnecting therefrom a user terminal whose connection status to the other user terminals in the network is unstable or which is in a state of connection-disabled, thereby solving the above-described problem in the conventional peer-to-peer network game system, i.e., preventing a status of a game commonly executed by user terminals in the game system from being differently displayed on a screen of each of the user terminals.  
         [0012]     The present invention has the following features to achieve the object mentioned above. Note that reference numerals and the like indicated between parentheses are merely provided to facilitate the understanding of the present invention in relation to the drawings, rather than limiting the scope of the present invention in any way.  
         [0013]     A first aspect of the present invention is a computer-readable storage medium for storing a game program ( 20 ) which is, in a game system in which a plurality of game devices ( 10 ) transmit and receive game data to and from each other and each of the plurality of game devices performs game processes by using the game data received from other game devices, executed by each of the plurality of game devices. The game program causes a computer ( 11 ) of each of the plurality of game devices to function as communication partners list addition means (S 12 ), communication status determination means (S 30 ), first communication status information update means (S 32 ), communication status information transmission means (S 38 ), communication status information reception means (S 16 ), second communication status information update means (S 36 ) and communication partners list deletion means (S 42 ). The communication partners list addition means is for, when another game device is newly connected to a network, to which said each of the plurality of game devices belongs, as a new communication partner, adding the new communication partner to a communication partners list ( 21 ) which is a listing of communication partners of said each of the plurality of game devices, the communication partners list being retained in a storage section ( 12 ) of said each of the plurality of game devices. The communication status determination means is for determining, based on a reception status ( 23 ) a signal from each of the communication partners, whether or not a communication between said each of the plurality of game devices and each of the communication partners is possible. The first communication status information update means is for, based on a determination result provided by the communication status determination means, updating as necessary a piece of communication status information about said each of the plurality of game devices ( 22   a ) which is retained in the storage section and which shows whether or not the communication between said each of the plurality of game devices and each of the communication partners is possible. The communication status information transmission means is for regularly transmitting the piece of communication status information about said each of the plurality of game devices ( 22   a ) to the communication partners. The communication status information reception means is for receiving, from the communication partners, pieces of communication status information about the communication partners ( 22   b ), and storing the pieces of communication status information in the storage section. The second communication status information update means is for referring to the pieces of communication status information about the communication partners received by the communication status information reception means, and, when any of the pieces of communication status information about the communication partners indicates that a particular game device which is one of the communication partners is unable to perform communication, updating the piece of communication status information about said each of the plurality of communication devices ( 22   a ) such that the piece of communication status information indicates that the particular game device is unable to perform communication. The communication partners list deletion means is for referring to the piece of communication status information about said each of the plurality of game devices ( 22   a ) and the pieces of communication status information about the communication partners ( 22   b ) which are retained in the storage section, and, when all pieces of communication status information indicate that a particular game device which is one of the communication partners is unable to perform communication, deleting the particular game device from the communication partners list ( 21 ).  
         [0014]     As a modification example of the first aspect, the game program may further cause the computer of each of the plurality of game devices to function as: game data transmission/reception means (S 38 , S 16 ) for transmitting and receiving the game data to and from each of the communication partners specified by the communication partners list; and game processing means (S 23 ) for performing game processes in accordance with the game data received from each of the communication partners by the game data transmission/reception means.  
         [0015]     As another modification example of the first aspect, the game data transmission/reception means may regularly transmit and receive the game data.  
         [0016]     As still another modification example of the first aspect, the piece of communication status information about each of the plurality of game devices is transmitted to any of the communication partners by the communication status information transmission means of said each of the plurality of game devices at a same time when the game data is transmitted to said any of the communication partners by the game data transmission/reception means of said each of the plurality of game devices.  
         [0017]     As still another modification example of the first aspect, the piece of communication status information about each of the plurality of game devices may contain a list showing, from among the communication partners of said each of the plurality of game devices which are listed in the communication partners list, only communication partners which have been determined by the communication status determination means as being able to perform communication ( FIG. 7A ).  
         [0018]     As still another modification example of the first aspect, the communication status determination means may measure an elapsed time from a last reception of a signal from each of the communication partners, and may determine, based on whether or not the elapsed time has reached a predetermined period of time, whether or not a communication with said each of the communication partners is possible.  
         [0019]     A second aspect of the present invention is a game device used in a game system in which a plurality of game devices ( 10 ) transmit and receive game data to and from each other, and each of the plurality of game devices performs game processes by using the game data received from other game devices. The game device comprises communication partners list addition means ( 11 , S 12 ), communication status determination means ( 11 , S 30 ), first communication status information update means ( 11 , S 32 ), communication status information transmission means ( 11 , S 38 ), communication status information reception means ( 11 , S 16 ), second communication status information update means ( 11 , S 36 ) and communication partners list deletion means ( 11 , S 42 ).  
         [0020]     A third aspect of the present invention is a game processing method which a plurality of game devices, which transmit and receive game data to and from each other, each execute by using the game data received from other game devices. The game processing method comprises: a communication partners list addition step of, when another game device is newly connected to a network, to which each of the plurality of game devices belongs, as a new communication partner, adding the new communication partner to the communication partners list which is a listing of communication partners of said each of the plurality of game devices, the communication partners list being retained in a storage section of said each of the plurality of game devices; a communication status determination step of determining, based on a status of receiving a signal from each of the communication partners, whether or not a communication between said each of the plurality of game devices and each of the communication partners is possible; a first communication status information update step of, based on a determination result provided at the communication status determination step, updating as necessary a piece of communication status information about said each of the plurality of game devices which is retained in the storage section and which shows whether or not the communication between said each of the plurality of game devices and each of the communication partners is possible; a communication status information transmission step of regularly transmitting the piece of communication status information about said each of the plurality of game devices to the communication partners; a communication status information reception step of receiving, from the communication partners, pieces of communication status information about the communication partners, and storing the pieces of communication status information in the storage section; a second communication status information update step of referring to the pieces of communication status information about the communication partners received at the communication status information reception step, and, when any of the pieces of communication status information about the communication partners indicates that a particular game device which is one of the communication partners is unable to perform communication, updating the piece of communication status information about said each of the plurality of communication devices such that the piece of communication status information indicates that the particular game device is unable to perform communication; and a communication partners list deletion step of referring to the piece of communication status information about said each of the plurality of game devices and the pieces of communication status information about the communication partners which are retained in the storage section, and, when all pieces of communication status information indicate that a particular game device which is one of the communication partners is unable to be perform communication, deleting the particular game device from the communication partners list.  
         [0021]     In the present invention, each of the plurality of game devices in the game system ceases communicating with a game device which is currently unable to communicate with said each of the plurality of game devices only when said each of the plurality of game devices has confirmed, based on the communication status information received from the communication partners, that all of the communication partners specified by the communication partners list of said each of the plurality of game devices are prepared to cease communicating with the game device. This prevents, in a peer-to-peer network game system, e.g., the occurrence of a situation in which one game device performs game processes in accordance with game data received from three game devices, and another game device performs game processes in accordance with game data received from four game devices. Thus, differences are prevented from occurring among results of the game processes performed by the user terminals.  
         [0022]     These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]      FIG. 1  shows a configuration of a network game system as a preferred embodiment of the present invention;  
         [0024]      FIG. 2  is an exemplary configuration of a user terminal  10 ;  
         [0025]      FIG. 3  is an exemplary memory map of a RAM  12 ;  
         [0026]      FIG. 4  is a specific example of a communication partners list  21 ;  
         [0027]      FIG. 5  is a specific example of communication status information  22 ;  
         [0028]      FIG. 6  is a specific example of a frame counter  23 ;  
         [0029]      FIG. 7A  is a first variation of a data structure of the communication status information  22 ;  
         [0030]      FIG. 7B  is a second variation of the data structure of the communication status information  22 ;  
         [0031]      FIG. 7C  is a third variation of the data structure of the communication status information  22 ;  
         [0032]      FIG. 8  is a flowchart showing a sequence of processes performed by a CPU  11 ;  
         [0033]      FIG. 9  is a flowchart showing a sequence of a communication status information transmission process;  
         [0034]      FIG. 10  is a flowchart showing a sequence of a disconnection process;  
         [0035]      FIG. 11A  shows relationships among user terminals at a 204 th  frame;  
         [0036]      FIG. 11B  shows information retained in a RAM of each user terminal at the 204 th  frame;  
         [0037]      FIG. 12A  shows relationships among the user terminals at a 500 th  frame;  
         [0038]      FIG. 12B  shows information retained in the RAM of each user terminal at the 500 th  frame;  
         [0039]      FIG. 13A  shows relationships among the user terminals at a 502 th  frame;  
         [0040]      FIG. 13B  shows information retained in the RAM of each user terminal at the 502 th  frame;  
         [0041]      FIG. 14A  shows relationships among the user terminals at a 510 th  frame;  
         [0042]      FIG. 14B  shows information retained in the RAM of each user terminal at the 510 th  frame;  
         [0043]      FIG. 15A  shows relationships among the user terminals at a 512 th  frame;  
         [0044]      FIG. 15B  shows information retained in the RAM of each user terminal at the 512 th  frame;  
         [0045]      FIG. 16A  shows relationships among the user terminals at a 514 th  frame;  
         [0046]      FIG. 16B  shows information retained in the RAM of each user terminal at the 514 th  frame;  
         [0047]      FIG. 17A  shows relationships among the user terminals at a 516 th  frame;  
         [0048]      FIG. 17B  shows information retained in the RAM of each user terminal at the 516 th  frame;  
         [0049]      FIG. 18A  shows relationships among the user terminals at a 520 th  frame;  
         [0050]      FIG. 18B  shows information retained in the RAM of each user terminal at the 520 th  frame;  
         [0051]      FIG. 19A  is another diagram showing relationships among the user terminals at the 520 th  frame;  
         [0052]      FIG. 19B  is another diagram showing information retained in the RAM of each user terminal at the 520 th  frame;  
         [0053]      FIG. 20A  shows relationships among the user terminals at a 522 th  frame;  
         [0054]      FIG. 20B  shows information retained in the RAM of each user terminal at the 522 th  frame;  
         [0055]      FIG. 21A  is another diagram showing relationships among the user terminals at the 522 th  frame;  
         [0056]      FIG. 2l B is another diagram showing information retained in the RAM of each user terminal at the 522 th  frame;  
         [0057]      FIG. 22A  shows relationships among the user terminals at a 524 th  frame;  
         [0058]      FIG. 22B  shows information retained in the RAM of each user terminal at the 524 th  frame;  
         [0059]      FIG. 23A  shows relationships among the user terminals at a 526 th  frame;  
         [0060]      FIG. 23B  shows information retained in the RAM of each user terminal at the 526 th  frame;  
         [0061]      FIG. 24A  is another diagram showing relationships among the user terminals at the 526 th  frame;  
         [0062]      FIG. 24B  is another diagram showing information retained in the RAM of each user terminal at the 526 th  frame;  
         [0063]      FIG. 25A  shows relationships among the user terminals at a 528 th  frame;  
         [0064]      FIG. 25B  shows information retained in the RAM of each user terminal at the 528 th  frame;  
         [0065]      FIG. 26A  is another diagram showing relationships among the user terminals at the 528 th  frame;  
         [0066]      FIG. 26B  is another diagram showing information retained in the RAM of each user terminal at the 528 th  frame; and  
         [0067]      FIG. 27  shows relationships among game devices in a conventional peer-to-peer network game system in which a communication failure has occurred. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0068]     Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings.  
         [0069]      FIG. 1  shows a configuration of a game system as the preferred embodiment of the present invention. The game system comprises a plurality of user terminals (game devices)  10 . The plurality of user terminals transmit and receive game data to and from each other, and each user terminal performs game processes by using the game data received from the other user terminals.  
         [0070]      FIG. 2  shows an exemplary configuration of a typical user terminal  10 . The user terminal  10  includes a CPU  11 , RAM  12 , hard disk  13 , communication section  14 , input section  15  and a display section  16 . The CPU  11  loads, into the RAM  12 , a game program prestored in the hard disk  13 , and executes the program. Although an example in which the game program is prestored in the hard disk  13  is described here, the present invention is not limited thereto. The game program may be supplied to the user terminal  10  through an external storage medium such as a memory card, a cartridge or a DVD-ROM. Also, the game program may be supplied to the user terminal  10  through the communication section  14 . The CPU  11  executes a video game such as a racing game by executing the game program. The input section  15  is used for game operations. The display section  16  is used to display game images.  
         [0071]      FIG. 3  is an exemplary memory map of the RAM  12  of the user terminal  10 . The RAM  12  stores, in addition to a game program  20  having been loaded from the hard disk  13 , a communication partners list  21 , communication status information  22  and a frame counter  23 . The communication partners list  21 , communication status information  22  and frame counter  23  are updated as necessary in accordance with a progress of the game.  
         [0072]     The communication partners list  21  is a list showing user terminals to and from which the user terminal  10  transmits and receive game data (hereinafter, such user terminals are referred to as communication partners). For example, when the game system comprises four user terminals A, B, C and D, and communications among these four user terminals are normally performed, the communication partners list retained in the RAM of the user terminal A is as shown in  FIG. 4 .  
         [0073]     The communication status information  22  indicates whether communications between the user terminal  10  and communication partners thereof listed in the communication partners list  21  are possible. Note that, the user terminals in the game system transmit to and receive from each other the communication status information  22 . Each user terminal retains, in the RAM  12 , the communication status information  22  comprising communication status information  22   a  about said each user terminal and communication status information  22   b  received from communication partners (i.e., communication status information  22   b  about the communication partners).  FIG. 5  shows exemplary communication status information  22  retained in the RAM of the user terminal A.  
         [0074]     The frame counter  23  measures an elapsed time (counts the number of elapsed frames) from the last reception of a signal from each of the communication partners listed in the communication partners list  21 .  FIG. 6  shows an exemplary frame counter  23  retained in the RAM of the user terminal A. As described later, when the frame counter  23  of the user terminal A has counted, for any communication partner, the number of elapsed frames to a predetermined threshold value (e.g., 300), the user terminal A determines said any communication partner has become unable to communicate with the user terminal A. Note that, the threshold value may be changed as necessary in accordance with a progress of the game. For example, a threshold value, which is used when the game system is calling for entries to a racing game, may be different from a threshold value which is used when the racing game is being played.  
         [0075]     As described above, the communication status information  22  indicates whether communications between the user terminal  10  and the communication partners thereof listed in the communication partners list  21  are possible. Various data structures of the information  22  may be conceived.  FIGS. 7A, 7B  and  7 C respectively show three exemplary pieces of communication status information retained in the RAM of the user terminal A (three exemplary pieces of the communication status information  22   a  about the user terminal A) in the case where the communication between the user terminals A and B has failed in the game system comprising the four user terminals A, B, C and D.  FIG. 7A  is an example in which the communication status information  22   a  indicates, from among all communication partners listed in the communication partners list  21 , only communication partners with which the user terminal A can communicate.  FIG. 7B  is an example in which the communication status information  22   a  indicates, for each communication partner listed in the communication partners list  21 , whether or not the user terminal A can communicate with said each communication partner.  FIG. 7C  is an example in which the communication status information  22   a  indicates, from among all communication partners listed in the communication partners list  21 , only communication partners with which the user terminal A cannot communicate. It is assumed in the description below that the communication status information  22   a  has a data structure shown in  FIG. 7A .  
         [0076]     Hereinafter, a sequence of processes, which the CPU  11  of the user terminal  10  performs in accordance with the game program  20 , will be described with reference to FIGS.  8  to  10 .  
         [0077]      FIG. 8  is a flow chart showing a sequence of a main process. When the main process starts, the CPU first determines at step S 10  whether a connection between the user terminal  10  and another user terminal has been newly established. If the connection has been newly established, the process proceeds to step S 12 . If the connection has not been newly established, the process proceeds to step S 14 .  
         [0078]     At step S 12 , the CPU  11  adds, to the communication partners list  21  retained in the RAM  12 , the newly connected user terminal (to be specific, identification information indicating the newly connected user terminal).  
         [0079]     At step S 14 , a communication status information transmission process is performed. Hereinafter, the communication status information transmission process will be described in detail with reference to  FIG. 9 .  
         [0080]     At step S 26  of  FIG. 9 , the CPU  11  copies a content of the communication partners list  21  of the user terminal  10 , and overwrites, with said content, the communication status information  22   a  of the user terminal  10 .  
         [0081]     At step S 28 , the CPU  11  of the user terminal  10  adds 1 to a number counted by the frame counter  23  for each of the other user terminals.  
         [0082]     It is determined at step S 30  whether there exists any user terminal for which the number counted by the frame counter  23  has reached the predetermined threshold value (e.g., 300). When there exists such a user terminal, the process proceeds to step S 32 . When there does not exist such a user terminal, the process proceeds to step S 34 .  
         [0083]     At step S 32 , the CPU  11  deletes, from the communication status information  22   a  about the user terminal  10 , a user terminal for which the number counted by the frame counter  23  has reached the predetermined threshold value.  
         [0084]     The CPU  11  of the user terminal  10  determines at step S 34  whether any of pieces of communication status information received from the other user terminals, i.e., any of pieces of communication status information  22   b  stored in the RAM  12  which are about the communication partners, indicates a user terminal with which the user terminal  10  cannot currently communicate. When such a user terminal is indicated, the process proceeds to step S 36 . When such a user terminal is not indicated, the process proceeds to step S 38 . For example, if, in the case where the game system comprises four user terminals A, B, C and D, the user terminal B receives from the user terminal A the communication status information shown in  FIG. 7A , a determination result at step S 34  provided by the user terminal B is positive since the communication status information indicates that the user terminals A and C cannot communicate with each other.  
         [0085]     At step S 36 , the CPU  11  deletes, from the communication status information  22   a  about the user terminal  10 , a user terminal which is indicated, by any of pieces of communication status information  22   b  stored in the RAM  12  which are about the communication partners, as being unable to perform communication. In the above example, the CPU  11  of the user terminal B deletes the user terminal C from the communication status information  22   a  about the user terminal B.  
         [0086]     At step S 38 , the CPU  11  of the user terminal  10  transmits, to all communication partners listed in the communication partners list  21 , the communication status information  22   a  about the user terminal  10  together with game data (note that, the communication status information  22   a  is not necessarily transmitted with the game data) . In other words, transmitted here as the communication status information  22   a  is a list of user terminals which results from deleting, from the communication partners list  21  of the user terminal  10 , a user terminal which the user terminal  10  is in the process of ceasing communicating with and a user terminal which another user terminal is in the process of ceasing communicating with. When a transmission of the communication status information  22   a  is completed at step S 38 , the communication status information transmission process ends, and the main process proceeds to step S 16  of  FIG. 8 .  
         [0087]     It is determined at step S 16  whether the communication status information has been received from any of the communication partners. When the communication status information has been received, the process proceeds to step S 18 . When the communication status information has not been received, the process proceeds to step S 22 .  
         [0088]     At step S 18 , the CPU  11  overwrites, by using the communication status information received from said any of the communication partners, the communication status information  22   b  stored in the RAM  12  which is about said any of the communication partners.  
         [0089]     At step S 20 , the CPU  11  resets a number to 0, the number having been counted by the frame counter  23  for said any of the communication partners which is a source of the received communication status information.  
         [0090]     At step S 22 , a disconnection process is performed. Hereinafter, the disconnection process is described in detail with reference to  FIG. 10 .  
         [0091]     At step S 40  of the disconnection process in  FIG. 10 , the CPU  11  refers, in the RAM  12 , to apiece of communication status information about the user terminal  10  and pieces of communication status information received from the communication partners listed in the communication partners list  21 , and determines whether there is a user terminal which is indicated, in all pieces of communication status information, as being unable to perform communication. When there is such a user terminal, the disconnection process proceeds to step S 42 . When there is not such a user terminal, the disconnection process ends, and then the main process proceeds to step S 23  of  FIG. 8 .  
         [0092]     At step S 42 , the user terminal which is shown, in said all pieces of communication status information stored in the RAM  12 , as being unable to perform communication is deleted from the communication partners list  21 . As a result, game data and the communication status information cease being transmitted to the user terminal deleted from the communication partners list  21 . When step S 42  is completed, the disconnection process ends, and then the main process proceeds to step S 23  of  FIG. 8 .  
         [0093]     At step S 23 , the CPU  11  performs game processes in accordance with inputs from the input section  15  and game data received from each communication partner.  
         [0094]     It is determined at step S 24  whether the game has ended. When the game has ended, the main process ends. When the game has not ended, the main process returns to step S 10 , and steps S 10  to S 23  are repeatedly performed with a period of 1 frame ( 1/60 second) until the game ends.  
         [0095]     Thus, in the case where the user terminal  10  ceases communicating with a particular user terminal, the user terminal  10  performs the above-described steps, thereby confirming, based on the communication status information received from all of communication partners currently connected to the user terminal  10 , that the all of currently-connected communication partners are prepared to cease communicating with the particular user terminal, and then ceases communicating with the particular user terminal. This prevents differences from occurring among results of the game processes performed by the user terminals.  
         [0096]     It is described above that at step S 38  of  FIG. 9 , the user terminal  10  transmits at each frame, to all communication partners listed in the communication partners list  21 , the communication status information  22   a  together with the game data. However, the present invention is not limited thereto. Alternatively, the user terminal  10  may transmit the game data and the communication status information separately. Further alternatively, the user terminal  10  may sequentially transmit in a predetermined order, to a plurality of communication partners, the game data together with the communication status information. For example: a user terminal A first transmits the game data and communication status information to a user terminal B; when two frames have elapsed therefrom, the user terminal A transmits the game data and communication status information to a user terminal C; when two frames have elapsed therefrom, the user terminal A transmits the game data and communication status information to a user terminal D; and when two frames have elapsed therefrom, the user terminal A again transmits the game data and communication status information to the user terminal B.  
         [0097]     Hereinafter, a sequence of processes, which are performed when, in the game system comprising four user terminals A, B, C and D, a failure occurs on a communication line between the user terminals A and B, will be described in detail with reference to  FIGS. 11A  to  26 B. Here, it is assumed that each user terminal transmits the communication status information to one of communication partners thereof in rotation after every second frame (i.e., transmissions of the communication status information to all communication partners are performed with a 6-frame period). Also, it is assumed that a time lag in data communication is a 10-frame period.  
         [0098]      FIG. 11A  shows connection relationships among the user terminals at a 204 th  frame. At this point, a failure has not occurred to any communication lines among the user terminals.  FIG. 11B  shows information retained in the RAM of each of the user terminals at the 204 th  frame. For example, the communication partners list  21  retained by the user terminal A contains the user terminals B, C and D. In the frame counter  23  retained by the user terminal A, the number of frames counted for the user terminal B is  2 ; the number of frames counted for the user terminal C is 0; and the number of frames counted for the user terminal D is  4 . The user terminal A retains, as the communication status information  22   b  about communication partners thereof, the communication status information about the user terminals B, C and D. For example, the communication status information about the user terminal B contains the user terminals A, C and D, and the communication status information  22   a  about the user terminal A, which the user terminal A retains, contains the user terminals B, C and D.  
         [0099]     If a failure occurs, immediately after the 204 th  frame, on a communication line between the user terminals A and B, connection relationships among the user terminals and information retained in the RAM of each of the user terminals are as shown in  FIGS. 12A and 12B  at a 500 th  frame. Since the number counted for the user terminal A by the frame counter of the user terminal B reaches a predetermined threshold value (300) at the 500 th  frame, the user terminal B determines (to be more specific, the CPU of the user terminal B determines) that the user terminal A is currently unable to communicate with the user terminal B, and then deletes the user terminal A from the communication status information about the user terminal B. Note that, due to a timing of transmitting the communication status information and the time lag in data communication, terminals currently connected to the user terminal B are notified of such a deletion of the user terminal A from the communication status information about the user terminal B in a few or dozens of frames after the deletion is performed.  
         [0100]     At a 502 nd  frame, the connection relationships among the user terminals and the information retained in the RAM of each of the user terminals are as shown in  FIGS. 13A and 13B . Since the number counted for the user terminal B by the frame counter of the user terminal A reaches the predetermined threshold value (300) at this frame, the user terminal A determines that the user terminal B is currently unable to communicate with the user terminal A, and deletes the user terminal B from the communication status information about the user terminal A.  
         [0101]     At a 510 th  frame, the connection relationships among the user terminals and the information retained in the RAM of each of the user terminals are as shown in  FIGS. 14A and 14B . At this frame, the communication status information transmitted from the user terminal B is received by the user terminal C. Upon receiving the information, the user terminal C recognizes that the user terminal A has been deleted from the communication status information about the user terminal B, and then the user terminal C deletes the user terminal A from the communication status information about the user terminal C.  
         [0102]     At a 512 th  frame, the connection relationships among the user terminals and the information retained in the RAM of each of the user terminals are as shown in  FIGS. 15A and 15B . At this frame, the communication status information transmitted from the user terminal B is received by the user terminal D. Upon receiving the information, the user terminal D recognizes that the user terminal A has been deleted from the communication status information about the user terminal B, and then the user terminal D deletes the user terminal A from the communication status information about the user terminal D.  
         [0103]     At a 514 th  frame, the connection relationships among the user terminals and the information retained in the RAM of each of the user terminals are as shown in  FIGS. 16A and 16B . At this frame, the communication status information transmitted from the user terminal A is received by the user terminal C. Upon receiving the information, the user terminal C recognizes that the user terminal B has been deleted from the communication status information about the user terminal A, and the user terminal C deletes the user terminal B from the communication status information about the user terminal C.  
         [0104]     At a 516 th  frame, the connection relationships among the user terminals and the information retained in the RAM of each of the user terminals are as shown in  FIGS. 17A and 17B . At this frame, the communication status information transmitted from the user terminal A is received by the user terminal D. Upon receiving the information, the user terminal D recognizes that the user terminal B has been deleted from the communication status information about the user terminal A, and the user terminal D deletes the user terminal B from the communication status information about the user terminal D.  
         [0105]     At a 520 th  frame, the connection relationships among the user terminals and the information retained in the RAM of each of the user terminals are as shown in  FIGS. 18A and 18B . At this frame, the communication status information transmitted from the user terminal C is received by the user terminal D. Upon receiving the information, the user terminal D recognizes that the user terminal A has been deleted from the communication status information about the user terminal C, and that the user terminal A is not contained in the communication status information about the other communication partners of the user terminal D. Then, as shown in  FIG. 19B , the user terminal D deletes from the communication partners list thereof the user terminal A. As a result, as shown in  FIG. 19A , a connection between the user terminals A and D is disconnected.  
         [0106]     At a 522 nd  frame, the connection relationships among the user terminals and the information retained in the RAM of each of the user terminals are as shown in  FIGS. 20A and 20B . At this frame, the communication status information transmitted from the user terminal C is received by the user terminal A, and the communication status information transmitted from the user terminal D is received by the user terminal C. Upon receiving the information, the user terminal C recognizes that the user terminal A has been deleted from the communication status information about the user terminal D, and that the user terminal A is not contained in the communication status information about the other communication partners of the user terminal C. Then, as shown in  FIG. 21B , the user terminal C deletes from the communication partners list thereof the user terminal A. As a result, as shown in  FIG. 21A , a connection between the user terminals A and C is disconnected.  
         [0107]     At a 524 th  frame, the connection relationships among the user terminals and the information retained in the RAM of each of the user terminals are as shown in  FIGS. 22A and 22B . At this frame, the communication status information transmitted from the user terminal C is received by the user terminal B.  
         [0108]     At a 526 th  frame, the connection relationships among the user terminals and the information retained in the RAM of each of the user terminals are as shown in  FIGS. 23A and 23B . At this frame, the communication status information transmitted from the user terminal D is received by the user terminal B, and the communication status information transmitted from the user terminal C is received by the user terminal D. Upon receiving the information, the user terminal D recognizes that the user terminal B has been deleted from the communication status information about the user terminal C, and that the user terminal B is not contained in the communication status information about the other communication partners of the user terminal D. Then, as shown in  FIG. 24B , the user terminal D deletes from the communication partners list thereof the user terminal B. As a result, as shown in  FIG. 24A , a connection between the user terminals B and D is disconnected.  
         [0109]     At a 528 th  frame, the connection relationships among the user terminals and the information retained in the RAM of each of the user terminals are as shown in  FIGS. 25A and 25B . At this frame, the communication status information transmitted from the user terminal D is received by the user terminal C. Upon receiving the information, the user terminal C recognizes that the user terminal B has been deleted from the communication status information about the user terminal D, and that the user terminal B is not contained in the communication status information about the other communication partners of the user terminal C. Then, as shown in  FIG. 26B , the user terminal C deletes from the communication partners list thereof the user terminal B. As a result, as shown in  FIG. 26A , a connection between the user terminals B and C is disconnected.  
         [0110]     Thereafter, the game is played only by the user terminals C and D. Since the user terminal A no longer receives signals from the other user terminals, numbers, which are counted by the frame counter of the user terminal A respectively for the communication partners of the user terminal A, continuously increase. When the numbers respectively counted for the communication partners each have reached 300, the user terminal A ceases performing the game processes. Note that, the user terminal B operates here in a same manner as that of the user terminal A.  
         [0111]     While the invention has been described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is understood that numerous other modifications and variations can be devised without departing from the scope of the invention.