The explosive popularity of smartphones and mobile devices drives massive growth in the wide-area mobile data communication. Unfortunately, the current or near-future 3G/4G networks are deemed insufficient to meet the increasing data transfer demand. While opportunistic offloading of mobile data through Wi-Fi is an attractive option, the existing transport layer would experience frequent disconnections due to mobility, making it hard to support seamlessly reliable data delivery. As a result, many mobile applications either depend on ad-hoc downloading resumption mechanisms or redundantly re-transfer the same content when disruptions happen. In this paper, we present DTP, a disruption-tolerant, reliable transport layer protocol that masks the failures of the preferred network. Unlike previous disruption/delay-tolerant protocols, DTP provides the same semantics as TCP on an IP packet level when the mobile device is connected to a network while providing the illusion of continued connection even if the underlying physical network becomes unavailable. This would help the mobile application developers to focus on the application core rather than addressing the frequent network disruptions. It would also greatly reduce the phone network costs both to ISPs and end users. Our current implementation in UDP shows a comparable performance to that of TCP in network, and it greatly reduces the delay and power consumption when the mobile devices frequently switch from one network to another.