基于异构网络进程实时通信的研究

Research of Process Real-time Communication Based on Heterogeneous Networks

针对异构计算机网络的互联和网络实时通信这两方面的问题，提出了异构网络的同构化思想，讨论了网络实时通信的实现方法，并给出了异构网中解决进程实时通信问题的模型和方案。

For a long peried the computer networks consist of various kinds of computers or vdri-ous kinds of networks. It is very important that how to solve the problem of internetworking on heterogenoous networks, and real-time cotnrnunication between computers is also a hotspot in net-work applications. In this paper, an idea of 'homogeneous translation of heterogeneous netwoks'is advanced, the implementation method df real-time communication is discussed, and the model and scheme to solve the problems are also provided.The 'homogneous translation of heterogeneous networks'can be divided into two idea lay-ers. The first is called'homogeneous translation on network layer'and the second is called 'homo-geneous translation on interface layer'.The realization of homogneous 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 dif-ferent systems which use TCP/IP protocols, at the view of programmer, all the networks are TCP/IP networks. On the other hand, our final obective is to cornmunicate between applications,and the application access TCP/IP must go via socket.The sockets of different systems are distinct, so the 'hornogencous translation on interface layer'is to solve the problem.The idea of 'homognans translation of heterogeneous networks'mentioned abe, 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 hardwar, but the real-time is related to the transfe nde. The implementation methed which is discued 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 probols in vdrious 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 sys-tem functidn call. Some important ones are as follows:(1)Create socket-socket()(2)Specify local address-bind()(3)Establish socket cormection-connect () & accept ()(4) Listen connection request-listen()(5 )Send date-write(), writev(), send() /Sendto(), sendmsg()(6)Receive date-read(), readv(), recv() /recvfrom(), recvtnsg()3) Use Client/Server modelThe experienced methed 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 processe in network must have a 'handshake'course before tranfer data, one requests and the other responses. When the 'handshake' course is suc-cessul, 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.