There is disclosed a method, computer program and bridge for linking two publish/subscribe message brokers together. A subscription is made to receive request messages on one or more topics from a first broker. A subscription is made to receive all messages published at either the first or the second broker to a replyto topic including a bridge identifier. A request message is received from the first broker, the request message specifying a temporary replyto topic on which responses to the request should be published. The temporary reply to topic is modified to specify a bridge identifier. The modified request message is forwarded to a second broker. A response to the request is received from the second broker, the response being published on the replyto topic including the bridge identifier. The bridge receives the response as a result of the subscription to receive all messages published to a topic including the bridge identifier. The response is forwarded to the first broker.