With the network popularization, applications on network are increasing day by day. VoIP (Voice over IP) is one of exciting developments on network applications, and its voice quality has been as good as traditional phones. Furthermore, IP phone users do not afford expensive communication costs, but go to the expense of broadband service. Therefore, more and more people start to use IP phone. After meeting certain requirements of basic communication, users could ask for more additional services. In the thesis, a voicemail service is built under SIP (Session Initiation Protocol). Users can keep missing call by recording voice with digital files, and then, one can receive recorded files from E-mail. Besides, small social networks can communicate with IP phones by using pear-to-pear telephony, which costs less money and labor due to no cost on building servers.