Research of Process Real-time Communication Based on Heterogeneous Networks

For a long period the computer networks consist of various kinds of computers or various kinds of networks. It is very important that how to solve the problem of internetworking on heterogeneous networks, and real-time communication between computers is also a hotspot in net-work applications. In this paper, an idea of "homogeneous translation of heterogeneous networks"is advanced, the implementation method of real-time communication is discussed, and the model and scheme to solve the problems are also provided.The "homogeneous translation of heterogeneous networks"can be divided into two idea layers. The first is called"homogeneous translation on network layer"and the second is called "homogeneous translation on interface layer".The realization of homogeneous translation on network layer is to use TCP/IP protocols. Be-cause most operation systems now support TCP/IP protocols,so if the programs are based on different systems which use TCP/IP protocols, at the view of programmer, all the networks are TCP/IP networks. On the other hand, our final objective is to communicate between applications,and the application access TCP/IP must go via socket.The sockets of different systems are distinct, so the "homogeneous translation on interface layer"is to solve the problem.The idea of "homogeneous translation of heterogeneous networks" mentioned above, greatly predigests the design and implementation of the communication on heterogeneous networks. This paper provides a path to resolve the problems.Real-time communications need transfer a mass of high-speed data between computers through networks. High-speed and real-time are the characters. That is said the transfer speed is high and the delay is dinky. In general, the speed lies on the hardware, but the real-time is related to the transfer mode. The implementation method which is discussed in this paper can be reduced to three processes.1) Internetworking with TCP/IPThe key of Internetworking with TCP/IP is to load TCP/IP protocols in various systems.Because programmer directly accesses network operation system, so they can avoid the hardware of networks. To load protocols in different system, the way is different, but the core is to provide a protocol stack. It is very easy to install and configure TCP/IP in Windows 95/98/NT. The steps are:open control panel, double click NETWORK icon, add Microsoft's TCP/IP protocol, then in the property dialog, input the IP address and subnet Mask, restart the computer.2)Use Berkeley socket as development interface Although the socket standard in different systems is various, but they have a intersection.That is the Berkeley socket. It is to say, all the socket standards support Berkeley socket. In spite of the difference in internal mechanism of socket, what is provided to programmer is a series system function call. Some important ones are as follows:(1)Create socket-socket()(2)Specify local address-bind()(3)Establish socket connection-connect () accept ()(4) Listen connection request-listen()(5)Send date-write(), writev(), send()/Sendto(), sendmsg()(6)Receive date-read(), readv(), recv()/recvfrom(), recvnsg()3) Use Client/Server modelThe experienced method to realize real-time communication is to use the end-to-end mode. To establish a end-to-end mode communication, the Client-Server model can be employed. Because the kernel of Client/Server model is that two processes in network must have a "handshake"course before transfer data, one requests and the other responses. When the "handshake" course is successful, a virtual circuitry is established between the quits layer from communication-source to communication-terminal, then the data transfer is on the circuitry, the middle mode exist or can not be ignored.