Communication control device and communication system

A communication control device controlling communication performed by a communication device having a message transmission part periodically transmitting messages, comprising:

• a reference time point decision part deciding a reference time point concerning message transmission by the message transmission part;
• a permission period decision part deciding that a predetermined period including a scheduled transmission time point obtained by adding a period corresponding to an integer multiple of a cycle of message transmission by the message transmission part to the reference time point decided by the reference time point decision part is a permission period for message transmission;
• a message detection part detecting a message transmitted by the communication device;
• and
• a transmittability determination part determining transmittability of a message detected by the message detection part in accordance with whether or not the message is transmitted during the permission period decided by the permission period decision part.

A communication system comprising a plurality of communication devices transmitting and receiving messages to/from each other, and a communication control device controlling communication performed by the communication devices, wherein:

• each communication device includes a message transmission part periodically transmitting messages, and
• the communication control device includes:
• a reference time point decision part deciding a reference time point concerning message transmission by the message transmission part;
• a permission period decision part deciding that a predetermined period including a scheduled transmission time point obtained by adding a period corresponding to an integer multiple of a cycle of message transmission by the message transmission part to the reference time point decided by the reference time point decision part is a permission period for message transmission;
• a message detection part detecting the message transmitted by a communication device;
• and
• a transmittability determination part determining transmittability of a message detected by the message detection part in accordance with whether or not the message is transmitted during the permission period decided by the permission period decision part.