Peer-to-peer (P2P) paradigm is the trend toward present Internet communication. However, the massive traffic of P2P file sharing has a deep and negative impact on mobile computing. Frequent and repeated file transmissions for different peers congest the wireless network. Request bursts may consume a mobile device 's computation power, energy, and other resources while certain of them may become ineffectual requests to waste the network bandwidth because of failing to find the wanted data in the target mobile device. In the paper, we propose the Object Proxy Service (OPS) for P2P file sharing in mobile computing. The OPS can cache data and serve requests on behalf of mobile devices to conserve wireless network bandwidth and mobile devices' computation power, energy, and other resources. We implement the OPS on the Java Applications' Packet Eavesdropper (JAPE) proposed previously. Besides, we develop a general P2P protocol to emulate the behaviors of current P2P file sharing and test it with the OPS. The experiments show that the OPS with linear scalability can serve requests on behalf of mobile devices to avoid the P2P traffic from being propagated over the wireless network. We are convinced that the OPS is suitable to work in a P2P community to conserve wireless network bandwidth and resources on mobile devices.