1. Summary
The sip server (server software composed of server functions such as proxy, registration, and redirection described in the previous article) is built based on the Linux operating system, which requires downloading a virtual machine in the windows operating system, and then it can be used in the virtual machine Linux operating system. There are many open source SIP servers, such as opensips, Asterisk, Kamailio, etc. There are many Linux operating systems that can be used, such as Ubuntu, CentOs, etc.
The Linux operating system used here is Ubuntu, and the open source sip server is opensips. The general steps are to install a virtual machine (VMware), then install Ubuntu in the virtual machine, and finally build the opensips network session server under the Ubuntu system.
2. Virtual machine
A virtual machine is a computer system that simulates a complete system hardware function through software . The so-called complete system hardware function refers to the underlying hardware resources (hard disk, memory, etc.) of the computer system. Therefore, when configuring a virtual machine, it is necessary to use part of the hardware and memory capacity of the physical computer (host) as the hard disk and memory capacity of the virtual machine.
The picture above shows the hardware configuration of an Ubuntu virtual machine, where NAT is network address translation, which allows an entire organization to appear on the network with a public IP address (allowing the virtual machine to share an IP with the physical host). NAT allows the internal network using private addresses to connect to the Internet or other IP networks. The method is to convert the private address into a legal IP address in the header of the IP packet when sending the data packet of the internal network to the public network. In addition, there are bridged, host-only and other modes. CD/DVD is the ISO image file that is selected for connection. There are two versions of Ubuntu, namely the server version and the desktop version. For server-side development, you must choose the server version.
Although the virtual machine is just a piece of software, it plays a very important role in reality.
*Multiple virtual machine operating systems can be installed in the same physical computer, and different operating systems can be experienced, used and tested;
*Penetration testing, vulnerability scanning and other training can be carried out, without worrying about the crash of the host system caused by improper operation;
* The game can be opened simultaneously on the same computer through a virtual machine;
*Can solve the problem that the computer does not have an optical drive through a virtual machine;
*The virtual machine system crashes only the operating system on the virtual machine, which can be quickly restored to the state before the crash through the snapshot function of the virtual machine, and in this series of operations, the physical machine is not affected in any way.
