Because of Internet routing fundamentals, mobile devices' network configurations have to be adjusted to correspond with the visited network. No matter people adjust it manually or let mobile devices do it automatically, the trouble unavoidably interrupts the continuity of network access. Although many solutions have been proposed, they need people to install related software in mobile devices. Installing related software in mobile devices may be undesired or unavailable due to resource limitations, policy constraint, or budget considerations. In the paper we propose the Unsolicited Relay NETwork (URNET) for mobile computing. The URNET uses a relay server to provide mobile devices with the service of continuous network access. Mobile devices need neither the installation of additional software nor the adjustment of network configuration to roam around the UKNETs. Applications and remote servers do not need to be modified either. We implement the relay server of the URNET in Windows 2000 and have related tests. The tests show that mobile devices can roam around URNETs without any configuration, installation, and modification. Meanwhile, the performance can meet the throughput of IEEE 802.11b wireless LAN when the relay server is deployed at the fixed network connected with 100 Mbps Ethernet.