Remote procedure calls in Unity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a remote procedure call method in Unity.

Unity

[[1]]
public void SendMessageToServer(string message) {
    Debug.Log(message);
}

Drag options to blanks, or click blank then click option'

ARPC

BPunRPC

CRemoteCall

DNetworkCall

Attempts:

3 left

💡 Hint

Common Mistakes

Using [RPC] instead of [PunRPC]

Forgetting the attribute entirely

Using a non-existent attribute like [RemoteCall]

In Unity with Photon, the attribute [PunRPC] marks a method as a remote procedure call.

2fill in blank

medium

Complete the code to call a remote procedure on all connected clients.

Unity

photonView.[1]("SendMessageToServer", RpcTarget.All, "Hello everyone!");

Drag options to blanks, or click blank then click option'

AInvokeRPC

BCallRemote

CRPC

DSendRPC

Attempts:

3 left

💡 Hint

Common Mistakes

Using a method name like CallRemote or SendRPC which do not exist

Trying to call the method directly without photonView

The method photonView.RPC is used to call remote procedures on clients.

3fill in blank

hard

Fix the error in the remote procedure call method declaration.

Unity

[PunRPC]
public void [1](string message) {
    Debug.Log(message);
}

Drag options to blanks, or click blank then click option'

ASendMessageToServer

BSend_Message

CSendMessageToServer()

DsendMessageToServer

Attempts:

3 left

💡 Hint

Common Mistakes

Including parentheses in the method name

Using camelCase instead of PascalCase

Using underscores in method names

Method names should not include parentheses in declaration and should follow PascalCase by convention.

4fill in blank

hard

Fill both blanks to create a dictionary that maps player names to their scores.

Unity

var highScores = new Dictionary<string, int> { { [1], [2] } };

Drag options to blanks, or click blank then click option'

A"playerName"

Bscore

CplayerScore

D"score"

Attempts:

3 left

💡 Hint

Common Mistakes

Using variable names that are not defined

Using quotes incorrectly around keys or values

The dictionary keys should be player names as strings and values should be the score variable.

5fill in blank

hard

Fill all three blanks to send a remote call only if the player score is greater than 50.

Unity

if ([1] [2] 50) {
    photonView.[3]("UpdateScore", RpcTarget.All, playerScore);
}

Drag options to blanks, or click blank then click option'

AplayerScore

B>

CRPC

Dscore

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong variable name in the condition

Using incorrect comparison operators

Using a wrong method name instead of RPC

The condition checks if playerScore is greater than 50, then calls photonView.RPC to update score remotely.

Practice

1. What attribute do you use in Unity to make a method run on the server when called from a client?

easy

A. [ServerRpc]

B. [ClientRpc]

C. [RunOnServer]

D. [RemoteCall]

Solution

1. Step 1: Understand the direction of the call

   Client-to-server calls require a special attribute to mark the method that runs on the server.

2. Step 2: Identify the correct attribute in Unity

   Unity uses [ServerRpc] to mark methods that clients call to run on the server.

3. Final Answer:

   [ServerRpc] -> Option A

4. Quick Check:

   Client-to-server calls use [ServerRpc] [OK]

Hint: Client calls server methods with [ServerRpc] attribute [OK]

Common Mistakes:

• Confusing [ClientRpc] as client-to-server
• Using non-existent attributes like [RunOnServer]
• Thinking [RemoteCall] is a valid Unity attribute

2. Which of the following is the correct syntax to declare a server RPC method in Unity?

easy

A. public void MyMethod() { }

B. [ServerRpc] public void MyMethod() { }

C. [ClientRpc] public void MyMethod() { }

D. void [ServerRpc] MyMethod() { }

Solution

1. Step 1: Recall the attribute placement

   Attributes in C# go before the method declaration.

2. Step 2: Check the correct attribute and syntax

   The correct syntax is [ServerRpc] public void MyMethod() { }. void [ServerRpc] MyMethod() { } places the attribute incorrectly.

3. Final Answer:

   [ServerRpc] public void MyMethod() { } -> Option B

4. Quick Check:

   Attributes precede method declarations [OK]

Hint: Attributes go before method signature in C# [OK]

Common Mistakes:

• Placing attribute after method name
• Using [ClientRpc] for server RPC
• Omitting the attribute entirely

3. Consider this Unity code snippet:

[ServerRpc]
public void SendMessageToClients(string msg) {
    Debug.Log("Server received: " + msg);
    BroadcastMessageClientRpc(msg);
}

[ClientRpc]
void BroadcastMessageClientRpc(string message) {
    Debug.Log("Client received: " + message);
}

What will be printed on the client when SendMessageToClients("Hello") is called from a client?

medium

A. Server received: Hello
Client received: Hello

B. Server received: Hello

C. Client received: Hello

D. Nothing is printed on client

Solution

1. Step 1: Understand the call flow

   The client calls SendMessageToClients which runs on the server due to [ServerRpc]. The server logs "Server received: Hello".

2. Step 2: Server calls client method

   The server then calls BroadcastMessageClientRpc on all clients, which logs "Client received: Hello" on each client.

3. Final Answer:

   Client received: Hello -> Option C

4. Quick Check:

   ClientRpc runs on clients, so clients see "Client received: Hello" [OK]

Hint: Client sees ClientRpc logs, server sees ServerRpc logs [OK]

Common Mistakes:

• Thinking server logs appear on client
• Assuming both logs print on client
• Confusing which method runs where

4. What is wrong with this Unity RPC method?

[ServerRpc]
public void UpdateScoreClientRpc(int score) {
    Debug.Log("Score updated: " + score);
}

medium

A. [ServerRpc] methods must be private

B. Missing return type for RPC method

C. RPC methods cannot have parameters

D. Method name suggests client RPC but uses [ServerRpc] attribute

Solution

1. Step 1: Analyze method name and attribute

   The method name contains "ClientRpc" but the attribute is [ServerRpc], which is confusing and likely a mistake.

2. Step 2: Check RPC method rules

   RPC methods can have parameters and must have a return type (void is valid). They can be public. The mismatch between name and attribute is the main issue.

3. Final Answer:

   Method name suggests client RPC but uses [ServerRpc] attribute -> Option D

4. Quick Check:

   Method name and attribute must match RPC direction [OK]

Hint: Match method name with RPC attribute to avoid confusion [OK]

Common Mistakes:

• Ignoring method name and attribute mismatch
• Thinking parameters are not allowed
• Assuming RPC methods must be private

5. You want to send a message from the server to all clients except the one who sent the original request. Which approach using Unity RPCs is correct?

hard

A. Use [ClientRpc] with a special NetworkConnection parameter to exclude sender

B. Use [ServerRpc] to send message to clients except sender

C. Use [ClientRpc] and check inside the client to ignore messages from itself

D. Use [ClientRpc] with a parameter to exclude the sender client inside the method

Solution

1. Step 1: Understand RPC direction

   Server sends messages to clients using [ClientRpc]. To exclude a client, the server must know which client to exclude.

2. Step 2: Use NetworkConnection parameter

   Unity allows [ClientRpc] methods to take a NetworkConnection parameter to exclude that client from receiving the RPC.

3. Step 3: Confirm other options

   Use [ClientRpc] with a parameter to exclude the sender client inside the method is incorrect because exclusion logic cannot be done inside the client method. Use [ServerRpc] to send message to clients except sender is wrong direction. Use [ClientRpc] and check inside the client to ignore messages from itself relies on client ignoring messages, which is inefficient.

4. Final Answer:

   Use [ClientRpc] with a special NetworkConnection parameter to exclude sender -> Option A

5. Quick Check:

   Exclude sender with NetworkConnection parameter in ClientRpc [OK]

Hint: Exclude sender using NetworkConnection param in ClientRpc [OK]

Common Mistakes:

• Trying to exclude sender inside client code
• Using ServerRpc to send to clients
• Not using NetworkConnection parameter for exclusion