Many of the existing works in wireless networks assumes that individual wireless node (possibly owned by selfish users) will follow prescribed protocols without deviation. In this paper, we address the issue of user cooperation in selfish and rational wireless networks using an incentive approach. We first present a strategy-proof pricing mechanism for the unicast problem and give a time optimal method to compute the payment in a centralized manner. We then discuss in detail how to implement the algorithm in the distributed manner. We conduct extensive simulations to study the relation of the total payment of a node to the total cost of all relay nodes and found out the ratio of the total payment over the total cost is small. Our protocol works when the wireless nodes will not collude and we show that no truthful mechanism can avoid the collusion between arbitrary two nodes. We also give truthful mechanism when a node only colludes with its neighbors.