Author: Hunter Spragg

• Version: February 2023

Purpose

To demonstrate using advanced Java features along with good object-oriented design to create a simple Client-Server JSON protocol. The goal of which is to Demonstrate a modular way of approaching Java server protocols.

• Please run gradle Server and gradle Client together.

Usage:

By default, the server will run on port 8888.
And the Client will connect to localhost on port 8888.
To change the port, use the -Pport=<int> flag.
To change the host, use the -Phost=<string> flag.

• For example, gradle Server -Pport=9999 will run the server on port 9999.
• For example, gradle Client -Phost=localhost -Pport=9999 will connect to the server on port 9999.

Protocol Specification:

The protocol is a simple JSON protocol.
In order to implement the protocol, you must send an integer containing the length of the JSON string you are sending. (4 bytes)
Then you must send the JSON string itself.

Client-To-Server:

{
  "operation": 1
}

• operation is the operation ID you wish the server to perform. (Integer)
  • See below for the full list of Protocols.

Supported Protocols:

• 1 - "Hypotenuse", returns the hypotenuse of a right triangle.

Example of Shutdown Protocol:

{
  "operation": 0
}

• 0 - "Shutdown", shuts down the connection between the client and server.

Example of Hypotenuse Protocol:

Client-To-Server:

{
    "operation": 1,
    "a": 5,
    "b": 10.5
}

• operation Represents the operation ID. (1)
• a Represents the first side of the triangle. (Number)
• b Represents the second side of the triangle. (Number)

Server-To-Client:

{
    "operation": 1,
    "a": 5,
    "b": 10.5,
    "result": 11.629703349613008
}

• operation Represents the operation ID. (1)
• a Represents the first side of the triangle. (Number)
• b Represents the second side of the triangle. (Number)
• result Represents the result of the operation. (Double)

Error Response Format:

{
    "error": -1,
    "message": "Error Message"
}

• error Represents the error code. (Integer)
• message Represents the error message. (String)

Error Codes:

• -1 - Internal Server/Client Error
  • This error is used when the server or client encounters a java error.
• 0 - Malformed Json
  • This error is used when the server or client receives malformed JSON string.
• 1 - Unsupported common.Operation
  • This error is used when the server or client receives an unsupported operation ID.
• 2 - Illegal Argument Type
  • This error is used when the server or client receives an argument of the wrong type.
• 3 - Missing Required Argument Type
  • This error is used when the server or client receives a missing argument.