With the advances in wireless communication technology and artificial intelligence, robots are gradually being introduced as part of our life. Previous research proposed a SIP-enabled Surveillance Patrol Robot (SSPR), which tracks a moving object actively and informs the householder of such security alarm. However, the underlying signaling protocol for communication and data streams suffer from the network address translation (NAT) traversal problem as most peer-to-peer (P2P) applications. NAT is a commonly adopted technique to share one public IPv4 address among several hosts located behind a NAT device for alleviating the exhaustion of IPv4 address. NAT devices typically block session requests originating from outside, prevent the establishment of peer-to-peer (P2P) sessions and cause NAT traversal problem. This study proposes WANTS, a WiFi Assisted NAT Traversal Scheme for SSPR. When SSPR is activated, it retrieves the topology information from a server to choose the candidate access point (AP) for handoff. Then SSPR uses the collected network context information to assist its NAT traversal procedure after handoff. Experimental results confirm that WANTS reduces not only connectivity check delay but also protocol messages as compared to the Interactivity Connectivity Establishment (ICE), which is the most acknowledged approach to creating a session across NATs.