With the dev elopmen t of Internet of Things (IoT), bridging wireless sensor netw orks (WSNs) with other netw orks has become importan t. We divide bridging solutions into tw o categ ories: the hardw are solutions and the middlew are solutions. The hardw are solutions have both low pow er short distance wireless interf aces and other types of transmission interf aces, e.g. GPRS, 3G/4G, via hardw are implemen tations, which is more stable and applicable for the depl oyed sensor netw orks. In the middlew are solutions, the whole system processes appropria te protocol conversion, and independence of hardw are, making it easier to be reused in dieren t applica tions and netw orks. This paper brief y presen ts the implemen tation details and key poin ts of each solution. Particular ly, we deriv e the most appropria te situa tion for each solution from our comparisons and discussions in terms of evaluation applied to dieren t criteria.