## Task 2

### Structure
***
1. **lib:** .jar files downloaded from [apache](https://archive.apache.org/dist/ws/xmlrpc/binaries/). the downloaded file is extracted and the contents of the `lib` directory copied in here.
2. **out:** output binaries in packages `server` and `client`
3. **src:** source code in 2 packages `client` and `server`

### How to run
***
1. First we compile the code (in linux using the following command)
    ```bash
    # the "lib/*" tells jvm to include these libraries
    javac -cp "lib/*" -d out $(find src -name "*.java")
    ```

2. Then we start the server. again run the following command
    ```bash
    java -cp "out:lib/*" server.Server
    ```

3. And finaly we run the client as such
    ```bash
    java -cp "out:lib/*" client.Client
    ```


    ### inspecting packets using wireshark.
    ***
    #### Normal functions
    ***

    I installed wireshark-cli and run 
    ```bash
    sudo tshark -i lo -f "tcp port 8080" -z follow,tcp,ascii,0
    ```
    In Client program the interaction looked like this
    ```
    Enter an integer: 4
    Enter an integer: 6
    The sum is: 10
    ```
    And the output of wireshark was as follows

    ```xml
        POST /RPC2 HTTP/1.1
        Content-Type: text/xml
        User-Agent: Apache XML RPC 3.0 (Sun HTTP Transport)
        Cache-Control: no-cache
        Pragma: no-cache
        Host: localhost:8080
        Accept: */*
        Connection: keep-alive
        Content-Length: 195

        <?xml version="1.0" encoding="UTF-8"?>
        <methodCall>
            <methodName>sample.sum</methodName>
            <params>
                <param>
                    <value><i4>4</i4></value>
                </param>
                <param>
                    <value><i4>6</i4></value>
                </param>
            </params>
        </methodCall>

    HTTP/1.1 200 OK
    Server: Apache XML-RPC 1.0
    Connection: close
    Content-Type: text/xml
    Content-Length: 129

    <?xml version="1.0" encoding="UTF-8"?>
    <methodResponse>
        <params>
            <param>
                <value><i4>10</i4></value>
            </param>
        </params>
    </methodResponse>
    ```
	I believe this is the expected result.

    ***
    #### Intentional error
    I changed the messge call string to `sample.add` instead of the correct `sample.sum` and run the program. obviously it threw an exception. the http response from wireguard was as follows
    ```xml
    POST /RPC2 HTTP/1.1
    Content-Type: text/xml
    User-Agent: Apache XML RPC 3.0 (Sun HTTP Transport)
    Cache-Control: no-cache
    Pragma: no-cache
    Host: localhost:8080
    Accept: */*
    Connection: keep-alive
    Content-Length: 196

    <?xml version="1.0" encoding="UTF-8"?>
    <methodCall>
        <methodName>sample.add</methodName>
            <params>
                <param>
                    <value><i4>23</i4></value>
                </param>
                <param>
                    <value><i4>4</i4></value>
                </param>
            </params>
        </methodCall>

    HTTP/1.1 200 OK
    Server: Apache XML-RPC 1.0
    Connection: close
    Content-Type: text/xml
    Content-Length: 265

    <?xml version="1.0" encoding="UTF-8"?>
    <methodResponse>
        <fault>
            <value>
                <struct>
                    <member>
                        <name>faultCode</name>
                        <value><i4>0</i4></value>
                    </member>
                    <member>
                        <name>faultString</name>
                        <value>No such handler: sample.add</value>
                    </member>
                </struct>
            </value>
        </fault>
    </methodResponse>
    ```
    Again the expected results. I only tested it in one machine. so time will be done may be another time.