The invention enables a reliable end-to-end monitoring system by means of which the location of containers and other conditions related to the containers can be continuously or almost continuously monitored. The containers are equipped with such container units that are capable to co-operate with each other, which is especially needed in challenging radio environments. The co-operation of the container units is based on mesh network algorithms. Each container unit placed in a container includes a short range radio and a cellular network radio. Thus, the container unit is able to connect to two different types of communication networks. In addition, each container unit uses a certain connection set-up logic. When a set-up attempt results in a connection, the container transmits its message through the connection. The invention comprises the container unit, a mesh network composed of container units, and a system reporting container events.