Communications Mechanisms and Methodologies within the Unix - Research Paper Example

1 Introduction It is possible for an operating system to be matured as well as state of the art simultaneously? If it is UNIX, then the answer would be “Yes.” UNIX has contributed in the Information technology sector for the last 25 years. Millions of installations conducted on various platforms and UNIX has proved to be organized and scalable. UNIX invented in 1969, by the computer scientists Dennis Ritchie and Kenneth Thompson employed at AT&T bell labs. Operating systems are compared by their functionality and performance. UNIX has contributed immensely in recent years. UNIX communication capabilities has also contributed in High performance computing sector as a company named Computer Associated International implemented a powerful system “Advantage Gen (release 6.5)”on UNIX platform to speed up the development of J2EE applications and web services (UNIX Update, 2002). UNIX back end server support the automatic generation of enterprise java beans facilitated the development teams to develop the J2EE application more efficiently. By the UNIX fast XML proxy support, web services are developed in no time on a distributed system as compared to the previous server architecture. IBM 32 way UNIX servers were also launched in year 2001 with the code name “Regatta”. The microprocessor architecture comprises of 1 GHz 64 Bit Power 4. This UNIX server is capable of self-healing technology and to decrease system failures. The system is capable to divide into 16 virtual servers which enable the businesses to unite several machines in to one. (E- Week, 2001) The Client-server model of UNIX was the core components for the growth of Internet and reshaping of the distributed systems networks. Inter process communication in the UNIX operating system involves the connection between the system components logically and physically. It supports real time network applications which allow the user to exchange messages in an interactive session. UNIX is known as a command line interface due to nonexistence of a GUI environment Today UNIX is equipped with a GUI along with dynamic communication functionalities. Some of the registered UNIX products are HP-UX, IBM AIX, SCO UnixWare, SGI IRIX, Sun Solaris etc. 2 UNIX Communication Mechanism Features 2.1 Pipes Pipe is used to transfer information between two processes. The pipes are also called special files, which only save a limited amount of data. The pipe uses FIFO (First in First Out) mechanism to retrieve data. The data is written at one end of the pipe and can be read on the other end. The system cannot identify the processes at the other end of the pipe. The system also provides synchronization between reading and writing process. The system block the pipes already involved in processing data and constantly monitor the pipes to assure the processes are running at both ends of the pipes. The deadlock prevention is handled by the programmers. Pipes can be divided in to two categories: Named Pipes: They exist in the form of directories with complete permissions. Unrelated processes can use them. Un Named Pipes: They can only be used by related programs 2.2 PIPES FUNCTIONALITY IN UNIX UNIX has limited the pipes to 512 K. Write ( ) un buffered is used to add data to the pipes. The system assured that no interleaving will occur even if the pipes fill on a temporary basis. For the retrieval of data, read ( ) is used. The pipes ( ) call is used to rename un named pipes in UNIX. The command retrieves two pipes supporting bi directional communication. Pipe is used for sending the output of one process to another process as input. When a pipe process in initialized, both processes run concurrently and the system cannot assure on which sequence each process is allowed to run. UNIX communication mechanism manages the producer and the consumer issue, both processes proceed and the system provides automatic blocking when required. 3 Sockets For communication between processes, a channel or interface is required for them to communicate. Sockets provide the link for the processes to interact with each other. The sockets allow “bi directional” communication and follow these steps for communication: Create a Socket Trace the system name, port number of the server Start sending and receiving data 3.1 Types of Sockets Sockets can be divided on to two categories: Streams Stream sockets guarantees the delivery of data, in the same order as it is sent. In the process of stream socket, a connection is established, and the two ends must agree logically before sending the data. Datagram Datagram sockets do not guarantee reliable delivery of data. The connection between the two ends is not consistent. Each datagram is sent and processed separately. There is no flow control, and each datagram can use different paths to reach the destination. 4 Socket Functionality in UNIX In the early 1980s, Berkeley introduced a socket interface for UNIX. A comprehensive definition which will give clear understanding is published on www.wordiq.com which states “The Berkeley sockets application programming interface (API) comprises a library for developing applications written in the C programming language that access a computer network” These sockets allow general file system type access routines to be sent/ receive over the network connection. The sockets were totally protocol independent and do not require TCP / IP for communication, as it was a common way of communication. Berkeley’s sockets support asynchronous I/O. Whenever a socket is available, the kernel notify system to use it for the distribution of data. As the sockets supports asynchronous mode, a different methodology is used for using more than one socket for the processes to transit. Select ( ) system call is executed. UNIX with its remarkable features of communication solves the problem of the delaying of data due to non-active sockets while an active socket blocks another I/O transaction to take place. 4.1 Potential Solutions to the problems in UNIX Polling If all sockets are set to be non-blocking, the process can execute a loop that analyzes each socket to see if there is something to be read. If it is available it handles it. If the data is not available it goes on a sleep mode until the next time the socket is scheduled to be checked. The polling process is inefficient because it consumed lot of CPU time. Use Multiple Process The parent process can use fork () to create a child process for socket handling. This communication mechanism enables the processes to read from the port and block since the system will handle scheduling the processes most efficiently. However the child process must return to read data from the parent process via some other form of IPC Asynchronous I/O This functionality is not effective in UNIX since signals are very rare and expensive to catch. If more than one socket is using asynchronous I/O, there is a need to find out which socket the signal corresponds to. 5 UNIX E-Mail Utility Unix Email program can only send text messages. It does not support binary files for example images, word documents. For sending binary files other email programs can be used. UNIX consists of two kinds of programs that handle emails: User Agent: This program provides the interface and interacts with the users for sending and receiving emails. The message sending and retrieval is connected to the transfer agent. Transfer Agent: This program does not interact directly with the user. It routes the messages to the required destinations. 6 View User List Command Linux supports a command “Finger” which is used to see how many users are logged on to the system. The command gives details as follows: User name, Full name of the person associated with the username, Terminal name, Login time, Machine from where he has connected on a specific system and idle time. 7 The talk Command UNIX supports a simple chat feature which is implemented by a talk command. It means UNIX users can communicate with the UNIX users. The status of the users can be checked via “Finger” command. The command syntax is “talk (name of the user)” to initiate a chat session at the source side. The recipient should respond back with the same command including his username for establishing a connection. Once a session is created, the message will appear in the command prompt “Connection established”. 8 Conclusion UNIX operating system supports flexible operations and processes which are helpful for the end users as well as for the programmers. It provides a vast number of standard interfaces for faster development. UNIX also supports enhanced network support and real time application for the users for interaction on the distributed environment. UNIX distributed its operations and system processes over the network without using TCP / IP, and implemented its own protocol for communication of data on the distributed network. UNIX operating system proves to be proficient in “inter process” communication, network communication, user friendliness and simultaneously efficient and reliable. References (2002). Ohio supercomputing center to deploy hp linux supercomputer. UNIX Update, 13(12), 7. Retrieved from Computers & Applied Sciences Complete database. Popovich, K. (2001). IBM's new 32-way Unix server turns heads. eWeek, 18(38), 11. Retrieved from Computers & Applied Sciences Complete database Berkeley sockets - Definition. WordIQ.com. Retrieved August 16, 2010, from http://www.wordiq.com/definition/Berkeley_sockets Read More