1. A portable terminal comprising: a communication device configured to transmit or receive information; a display; and at least one processor configured to: control the display to display a messenger chat window after receiving an indication at the portable terminal to execute a messenger chat application, receive, from a second terminal, a first chat message corresponding to a second chat message previously transmitted from the portable terminal to the second terminal using the messenger chat application, the first chat message being transmitted by the second terminal and including index information associated with the second chat message, determine whether the second chat message is currently displayed in the messenger chat window based on the index information associated with the second chat message received from the second terminal, if the second chat message is currently displayed in the message chat window, control the display to display the first chat message directly adjacent to the second chat message in the message chat window, if the second chat message is not currently displayed in the message chat window, control the display to display a notification that the first chat message has been received, and if an input for displaying the first chat message is received in response to the notification that the first chat message has been received, retrieve the second chat message associated with the first chat message and control the display to display the first chat message and the second chat message within the messenger chat window after the input for displaying the first chat message is received.