IMPLEMENTATION OF ECHO SERVER

Abstract

Echo Service is a well known service running at port 7 for testing & debugging purposes. Our project was to develop an Echo Server. Echo server is a simple server which echoes sent by client back to it. Clients for these are also presented ,but with lesser focus. The application of the echo server suggests simplicity ,robustness & efficiency as prime requirements. Due Simplicity of application in case of echo server is synonymous with performance(simplicity reduces overhead) because of the simple nature of the service & the reasons namely testing for which it is used. Hence any extra overhead in the form of a complex algorithm or complex programming techniques like recursion, synchronization is avoided. Though for some special cases different approaches have been presented in brief. These are provided at the end in the section of suggestion for improvement. Four types of servers are there; we covered three(Connectionless-iterative ,Connection -oriented iterative ,connection oriented Concurrent(common) )while the fourth Connectionless concurrent is rare. Except the initial servers, rest was designed for robustness/efficiency or both. Each type fulfills different requirements to different degrees & hence, for different versions is developed. Echo service is mostly exploited by Ackers/malicious clients & hence, their vulnerabilities are discussed with possible solutions are provided for those within our scope. The first two servers developed by us are Connection oriented Concurrent TCP server(general Process based) & Connectionless Iterative UDP server(generally UDP servers are iterative).The next Server was a robust multi-mode version of the Concurrent TCP server with input validation, error checks , redundancy, acceptable behavior at boundary conditions, etc).The fourth one is a single process concurrent server to minimize resources based on I/O multiplexing. Lastly, the best option for an echo server ;the threaded server was used to reduce process forking overhead. The platform chosen was UNIX(posix.1g)/Linux owing to the efficiency & simplicity of these systems & the C language was used. 3