The invention relates to a communication system comprising at least one first communication network designed for communication according to a first protocol, at least one second communication network designed for communication according to a second protocol, and at least one third communication network designed for communication according to the first and second protocols. The at least one first communication network and/or the at least one second communication network and/or the at least one third communication network are coupled together for the exchange of messages. The inventive system also comprises a mobile computer designed for communication according to the first and second protocols, and a target computer which is designed for communication according to the first protocol and/or the second protocol, and is associated with the first, second or third communication network. The inventive communication system is designed in such away that when the mobile computer is connected to a network connection computer of the third communication network, before the establishment of a communication connection to the target computer, the protocol to be used for communication with the network connection computer is determined.