This image shows a desktop computer on the left, labeled "Host A" and a server on the right, labeled "Server B." Immediately to the right of Host A is an unlabeled five-layer protocol stack. In the top layer is a white oval, indicated to represent the "Client process." Beneath this, on the line between the top layer and the one below it, is a blue rectangle, indicated to represent the "Socket." A blue arrow extends from the client process, down through the layers of the protocol stack and to the right, where it turns upwards and connects with the Server B. A second blue arrow extends from Server B and travels the same route back to the client process. In the mid-point of this route, we see a blue data packet traveling towards Server B on one arrow and towards Host A on the other blue arrow. The blue data packet traveling towards Server B is labeled as such:

The blue data packet traveling towards Host A is labeled as such: