Submitted by: Prerna Gupta
Roll No: 143050021

##Introduction

This assignment is to build a simple file server, with a simple read/write interface. The file contents are stored in memory. The server listens on port 8080. Concurrent operations by multiple clients is taken into consideration.

##Installation Instructions

go get github.com/prernaguptaiitb/cs733-assign1

Folder contains two files: server.go(containing server code) and concurrency_test.go (containing test cases for the server)

Run the server : "go run server.go" .
Start the client : telnet localhost 8080
You can start multiple clients.

• Write: create a file, or update the file’s contents if it already exists.

write <filename> <numbytes> [<exptime>]\r\n
 <content bytes>\r\n

If expiry time not specified then file does not expires.

The server responds with the following: OK \r\n

• Read: Given a filename, retrieve the corresponding file:

read <filename>\r\n

The server responds with the following format if file is present at the server. CONTENTS \r\n \r\n

Here is the remaining time in seconds left for the file after which it will expire. If file is not present at the server, the server responds with ERR_FILE_NOT_FOUND.

• Compare and swap (cas): This replaces the old file contents with the new content provided the version is still the same.

cas <filename> <version> <numbytes> [<exptime>]\r\n
 <content bytes>\r\n

The server responds with the new version if successful :- OK \r\n If version does not match, server responds with :- ERR_VERSION \r\n

• Delete file

delete <filename>\r\n

Server response (if successful) OK\r\n

Server return following error messages :

• ERR_VERSION \r\n (the contents were not updated because of a version mismatch. The latest version is returned)
• ERR_FILE_NOT_FOUND\r\n (the filename doesn’t exist)
• ERR_CMD_ERR\r\n (the command is not formatted correctly)