Method for exchanging data between several field devices , wherein the field devices are in a communication link based on the publish-subscribe principle via a data broker with a broker functionality, wherein at least one field device publishes at least one message with a message title to the data broker , wherein at least one field device subscribes to a message with at least one specific component of a message title from the data broker , wherein the message sent to the data broker is received by the data broker and the data broker forwards the received message to the at least one field device , which field device has subscribed to the message with the respective component of the message title from the data broker wherein an exchange of data based on the request-response principle between a requesting field device and a responding field device is implemented by means of the publish-subscribe principle in that a unique field device identifier (F_Resp_ID) of the responding field device is made known at least to the requesting field device , wherein the responding field device subscribes (subscribe: f(F_Resp_ID)) to request messages whose message titles comprise a specification (f(F_Resp_ID)) of the field device identifier (F Resp ID) of the responding field device , wherein the requesting field device subscribes (subscribe: Req_ID) to response messages whose message titles comprise a request identifier (Req_ID) known to the requesting field device , wherein the requesting field device publishes a request message to the data broker , wherein the message title of the request message comprises the request identifier (Req_ID) and the specification (f(F_Resp_ID)) of the field device identifier (F_Resp_ID) of the responding field device , wherein the responding field device receives the request message from the requesting field device on the basis of the subscription to the request messages , evaluates the request message and publishes a corresponding response message to the data broker , wherein the message title of the response message comprises at least the request identifier (Req_ID), and wherein the requesting field device receives the response message of the responding field device based on the subscription to the response message . wherein an exchange of data based on the request-response principle between a requesting field device and a responding field device is implemented by means of the publish-subscribe principle in that a unique field device identifier (F_Resp_ID) of the responding field device is made known at least to the requesting field device , wherein the responding field device subscribes (subscribe: f(F_Resp_ID)) to request messages whose message titles comprise a specification (f(F_Resp_ID)) of the field device identifier (F Resp ID) of the responding field device , wherein the requesting field device subscribes (subscribe: Req_ID) to response messages whose message titles comprise a request identifier (Req_ID) known to the requesting field device , wherein the requesting field device publishes a request message to the data broker , wherein the message title of the request message comprises the request identifier (Req_ID) and the specification (f(F_Resp_ID)) of the field device identifier (F_Resp_ID) of the responding field device , wherein the responding field device receives the request message from the requesting field device on the basis of the subscription to the request messages , evaluates the request message and publishes a corresponding response message to the data broker , wherein the message title of the response message comprises at least the request identifier (Req_ID), and wherein the requesting field device receives the response message of the responding field device based on the subscription to the response message . <EOS>