Method for exchanging data between several field devices (2, 2a, 2b), wherein the field devices (2, 2a, 2b) 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 (2, 2a, 2b) publishes at least one message with a message title to the data broker, wherein at least one field device (2, 2a, 2b) 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.