diff --git a/api/src/main/java/net/azisaba/azipluginmessaging/api/entity/Player.java b/api/src/main/java/net/azisaba/azipluginmessaging/api/entity/Player.java
index 53e0aa0..dee0123 100644
--- a/api/src/main/java/net/azisaba/azipluginmessaging/api/entity/Player.java
+++ b/api/src/main/java/net/azisaba/azipluginmessaging/api/entity/Player.java
@@ -21,7 +21,7 @@ public interface Player {
     UUID getUniqueId();
 
     /**
-     * Sends a message to the player. This method might do nothing depending on the implementation.
+     * Sends a message to the player.
      * @param message the message
      */
     void sendMessage(@NotNull String message);
@@ -35,5 +35,11 @@ default String getUsernameOrUniqueId() {
         return getUsername() != null ? getUsername() : getUniqueId().toString();
     }
 
+    /**
+     * Checks if the player has the challenge equals to the provided challenge. Challenge token is used for securing
+     * initial encryption packet.
+     * @param challenge the challenge token to check
+     * @return true if the player has the challenge equals to the provided challenge
+     */
     boolean isChallengeEquals(@NotNull String challenge);
 }
diff --git a/api/src/main/java/net/azisaba/azipluginmessaging/api/entity/SimplePlayer.java b/api/src/main/java/net/azisaba/azipluginmessaging/api/entity/SimplePlayer.java
index a23defd..bcaf2dd 100644
--- a/api/src/main/java/net/azisaba/azipluginmessaging/api/entity/SimplePlayer.java
+++ b/api/src/main/java/net/azisaba/azipluginmessaging/api/entity/SimplePlayer.java
@@ -10,7 +10,8 @@
 import java.util.UUID;
 
 /**
- * Simple instance of {@link Player}.
+ * Simple instance of {@link Player}. It lacks most of the features, and for example, you can't send messages to this
+ * instance.
  */
 public final class SimplePlayer implements Player {
     private final UUID uuid;
diff --git a/api/src/main/java/net/azisaba/azipluginmessaging/api/protocol/PacketFlow.java b/api/src/main/java/net/azisaba/azipluginmessaging/api/protocol/PacketFlow.java
index 936f8e6..bc64a98 100644
--- a/api/src/main/java/net/azisaba/azipluginmessaging/api/protocol/PacketFlow.java
+++ b/api/src/main/java/net/azisaba/azipluginmessaging/api/protocol/PacketFlow.java
@@ -1,6 +1,12 @@
 package net.azisaba.azipluginmessaging.api.protocol;
 
 public enum PacketFlow {
+    /**
+     * Server (Backend) -> Proxy
+     */
     TO_PROXY,
+    /**
+     * Proxy -> Server (Backend)
+     */
     TO_SERVER,
 }
diff --git a/api/src/main/java/net/azisaba/azipluginmessaging/api/protocol/PacketQueue.java b/api/src/main/java/net/azisaba/azipluginmessaging/api/protocol/PacketQueue.java
index 114b2a0..61e9ade 100644
--- a/api/src/main/java/net/azisaba/azipluginmessaging/api/protocol/PacketQueue.java
+++ b/api/src/main/java/net/azisaba/azipluginmessaging/api/protocol/PacketQueue.java
@@ -5,9 +5,22 @@
 import org.jetbrains.annotations.NotNull;
 
 public abstract class PacketQueue {
+    /**
+     * Empty packet queue that does nothing.
+     */
     public static final PacketQueue EMPTY = new Empty();
 
+    /**
+     * Adds the message to the queue.
+     * @param protocol The protocol.
+     * @param message The message.
+     */
     public abstract void add(@NotNull Protocol<?, ?> protocol, @NotNull Message message);
+
+    /**
+     * Removes the message from the queue and sends all messages to provided sender.
+     * @param sender the sender
+     */
     public abstract void flush(@NotNull PacketSender sender);
 
     private static class Empty extends PacketQueue {
diff --git a/api/src/main/java/net/azisaba/azipluginmessaging/api/protocol/Protocol.java b/api/src/main/java/net/azisaba/azipluginmessaging/api/protocol/Protocol.java
index 7852bf2..f4a95ed 100644
--- a/api/src/main/java/net/azisaba/azipluginmessaging/api/protocol/Protocol.java
+++ b/api/src/main/java/net/azisaba/azipluginmessaging/api/protocol/Protocol.java
@@ -45,7 +45,15 @@
 public final class Protocol<T extends MessageHandler<M>, M extends Message> {
     private static final Map<Byte, Protocol<?, ?>> TO_PROXY_BY_ID = new ConcurrentHashMap<>();
     private static final Map<Byte, Protocol<?, ?>> TO_SERVER_BY_ID = new ConcurrentHashMap<>();
+
+    /**
+     * Legacy plugin channel id
+     */
     public static final String LEGACY_CHANNEL_ID = "AziPluginMessaging";
+
+    /**
+     * Modern plugin channel id
+     */
     public static final String CHANNEL_ID = "azipm:main";
 
     public static final Protocol<ProxyboundEncryptionPacket, EncryptionMessage> P_ENCRYPTION = new Protocol<>(PacketFlow.TO_PROXY, 0x00, new ProxyboundEncryptionPacket());
@@ -65,6 +73,16 @@ public final class Protocol<T extends MessageHandler<M>, M extends Message> {
     private final byte id;
     private final T handler;
 
+    /**
+     * Creates a new packet. Handler should be a subclass of {@link ProxyMessageHandler} if packet flow is
+     * {@link PacketFlow#TO_PROXY}, and a subclass of {@link ServerMessageHandler} if packet flow is
+     * {@link PacketFlow#TO_SERVER}.
+     * @param packetFlow The packet flow
+     * @param id The packet id, must be unique in the packet flow
+     * @param handler The handler
+     * @throws IllegalArgumentException if the id is already registered
+     * @throws IllegalArgumentException if the handler is implementing wrong type for the packet flow
+     */
     private Protocol(@NotNull PacketFlow packetFlow, int id, @NotNull T handler) {
         this.packetFlow = packetFlow;
         this.id = (byte) (id & 0xFF);
@@ -74,7 +92,7 @@ private Protocol(@NotNull PacketFlow packetFlow, int id, @NotNull T handler) {
                 throw new IllegalArgumentException("Handler must be instance of ProxyMessageHandler");
             }
             if (TO_PROXY_BY_ID.containsKey(this.id)) {
-                throw new AssertionError("Duplicate protocol id: " + this.id);
+                throw new IllegalArgumentException("Duplicate protocol id: " + this.id);
             }
             TO_PROXY_BY_ID.put(this.id, this);
         } else {
@@ -82,7 +100,7 @@ private Protocol(@NotNull PacketFlow packetFlow, int id, @NotNull T handler) {
                 throw new IllegalArgumentException("Handler must be instance of ServerMessageHandler");
             }
             if (TO_SERVER_BY_ID.containsKey(this.id)) {
-                throw new AssertionError("Duplicate protocol id: " + this.id);
+                throw new IllegalArgumentException("Duplicate protocol id: " + this.id);
             }
             TO_SERVER_BY_ID.put(this.id, this);
         }
@@ -149,9 +167,11 @@ public boolean sendPacket(@Nullable PacketSender sender, @NotNull M msg) {
     }
 
     /**
-     * This method is called when a packet is received (proxy-side).
+     * This method is called when a raw packet is received (proxy-side).
      * @param server the server connection
      * @param rawData the data of the packet
+     * @throws RuntimeException if the connection is encrypted but cannot decrypt the packet
+     * @throws RuntimeException if the packet must be received encrypted but the connection is not encrypted
      */
     public static void handleProxySide(ServerConnection server, byte[] rawData) {
         byte[] data;
@@ -168,7 +188,7 @@ public static void handleProxySide(ServerConnection server, byte[] rawData) {
              DataInputStream in = new DataInputStream(bin)) {
             byte id = (byte) (in.readByte() & 0xFF);
             if (id != 0 && !server.isEncrypted()) {
-                throw new RuntimeException("Packet " + id + " must be sent encrypted (server: " + server + ")");
+                throw new RuntimeException("Packet " + id + " must be received encrypted (server: " + server + ")");
             }
             Protocol<?, ?> protocol = Protocol.getById(PacketFlow.TO_PROXY, id);
             if (protocol == null) {
@@ -183,7 +203,7 @@ public static void handleProxySide(ServerConnection server, byte[] rawData) {
                 Logger.getCurrentLogger().info("Received packet {} (0x{}) from server connection {} (encrypted: {})", id, hex, server, server.isEncrypted());
             }
             if (protocol.packetFlow != PacketFlow.TO_PROXY) {
-                throw new IllegalArgumentException("Packet " + protocol + " is not proxybound");
+                throw new AssertionError("Packet " + protocol + " is not proxybound");
             }
             @SuppressWarnings("unchecked")
             ProxyMessageHandler<Message> handler = (ProxyMessageHandler<Message>) protocol.getHandler();
@@ -195,8 +215,10 @@ public static void handleProxySide(ServerConnection server, byte[] rawData) {
     }
 
     /**
-     * This method is called when a packet is received (server-side).
+     * This method is called when a raw packet is received (server-side).
      * @param rawData the data of the packet
+     * @throws RuntimeException if the connection is encrypted but cannot decrypt the packet
+     * @throws RuntimeException if the packet must be received encrypted but the connection is not encrypted
      */
     public static void handleServerSide(@NotNull PacketSender sender, byte[] rawData) {
         byte[] data;
@@ -213,7 +235,7 @@ public static void handleServerSide(@NotNull PacketSender sender, byte[] rawData
              DataInputStream in = new DataInputStream(bin)) {
             byte id = (byte) (in.readByte() & 0xFF);
             if (id != 0 && !sender.isEncrypted()) {
-                throw new RuntimeException("Packet " + id + " must be sent encrypted (sender: " + sender + ")");
+                throw new RuntimeException("Packet " + id + " must be received encrypted (sender: " + sender + ")");
             }
             Protocol<?, ?> protocol = Protocol.getById(PacketFlow.TO_SERVER, id);
             if (protocol == null) {
@@ -226,7 +248,7 @@ public static void handleServerSide(@NotNull PacketSender sender, byte[] rawData
                 Logger.getCurrentLogger().info("Received packet {} (0x{}) from {}", id, hex, sender);
             }
             if (protocol.packetFlow != PacketFlow.TO_SERVER) {
-                throw new IllegalArgumentException("Packet " + protocol + " is not serverbound");
+                throw new AssertionError("Packet " + protocol + " is not serverbound");
             }
             @SuppressWarnings("unchecked")
             ServerMessageHandler<Message> handler = (ServerMessageHandler<Message>) protocol.getHandler();
@@ -237,6 +259,10 @@ public static void handleServerSide(@NotNull PacketSender sender, byte[] rawData
         }
     }
 
+    /**
+     * Returns the packet flow of this packet.
+     * @return the packet flow
+     */
     @NotNull
     @Contract(pure = true)
     public PacketFlow getPacketFlow() {
@@ -271,10 +297,15 @@ public PacketFlow getPacketFlow() {
         }
     }
 
+    /**
+     * Returns the protocol data in string form.
+     * @return the protocol data
+     */
     @Override
     public String toString() {
         return "Protocol{" +
                 "id=" + id +
+                ", packetFlow=" + packetFlow +
                 ", handler=" + handler +
                 '}';
     }
diff --git a/api/src/main/java/net/azisaba/azipluginmessaging/api/protocol/handler/ServerboundActionResponsePacket.java b/api/src/main/java/net/azisaba/azipluginmessaging/api/protocol/handler/ServerboundActionResponsePacket.java
index a7c5805..4574dda 100644
--- a/api/src/main/java/net/azisaba/azipluginmessaging/api/protocol/handler/ServerboundActionResponsePacket.java
+++ b/api/src/main/java/net/azisaba/azipluginmessaging/api/protocol/handler/ServerboundActionResponsePacket.java
@@ -9,6 +9,9 @@
 import java.io.IOException;
 import java.util.UUID;
 
+/**
+ * Sends the arbitrary message to a player.
+ */
 public class ServerboundActionResponsePacket implements ServerMessageHandler<ServerboundActionResponseMessage> {
     @NotNull
     @Override
@@ -20,6 +23,8 @@ public ServerboundActionResponseMessage read(@NotNull DataInputStream in) throws
 
     @Override
     public void handle(@NotNull PacketSender sender, @NotNull ServerboundActionResponseMessage msg) throws Exception {
-        AziPluginMessagingProvider.get().getPlayer(msg.getUniqueId()).ifPresent(player -> player.sendMessage(msg.getMessage()));
+        AziPluginMessagingProvider.get()
+                .getPlayer(msg.getUniqueId())
+                .ifPresent(player -> player.sendMessage(msg.getMessage()));
     }
 }
diff --git a/api/src/main/java/net/azisaba/azipluginmessaging/api/protocol/message/ServerboundActionResponseMessage.java b/api/src/main/java/net/azisaba/azipluginmessaging/api/protocol/message/ServerboundActionResponseMessage.java
index 8389769..072e8a5 100644
--- a/api/src/main/java/net/azisaba/azipluginmessaging/api/protocol/message/ServerboundActionResponseMessage.java
+++ b/api/src/main/java/net/azisaba/azipluginmessaging/api/protocol/message/ServerboundActionResponseMessage.java
@@ -10,16 +10,29 @@ public class ServerboundActionResponseMessage implements Message {
     private final UUID uuid;
     private final String message;
 
+    /**
+     * Creates a new instance.
+     * @param uuid The UUID of the player.
+     * @param message The message (may contain \u00a7).
+     */
     public ServerboundActionResponseMessage(@NotNull UUID uuid, @NotNull String message) {
         this.uuid = uuid;
         this.message = message;
     }
 
+    /**
+     * Gets the UUID of the player.
+     * @return the uuid
+     */
     @NotNull
     public UUID getUniqueId() {
         return uuid;
     }
 
+    /**
+     * Gets the message.
+     * @return the message
+     */
     @NotNull
     public String getMessage() {
         return message;
diff --git a/api/src/main/java/net/azisaba/azipluginmessaging/api/server/Connection.java b/api/src/main/java/net/azisaba/azipluginmessaging/api/server/Connection.java
new file mode 100644
index 0000000..553ed12
--- /dev/null
+++ b/api/src/main/java/net/azisaba/azipluginmessaging/api/server/Connection.java
@@ -0,0 +1,37 @@
+package net.azisaba.azipluginmessaging.api.server;
+
+import org.jetbrains.annotations.NotNull;
+
+import java.security.KeyPair;
+import java.security.PublicKey;
+
+/**
+ * Represents something that can have a connection.
+ */
+public interface Connection {
+    /**
+     * Marks the connection as encrypted.
+     * @param encrypted true if the connection is encrypted; false otherwise
+     */
+    void setEncrypted(boolean encrypted);
+
+    /**
+     * Checks if the connection is encrypted.
+     * @return true if the connection is encrypted; false otherwise
+     */
+    boolean isEncrypted();
+
+    /**
+     * Gets the local key pair for encrypting packets.
+     * @return the local key pair
+     */
+    @NotNull
+    KeyPair getKeyPair();
+
+    /**
+     * Gets the remote public key for decrypting packets.
+     * @return the remote public key
+     */
+    @NotNull
+    PublicKey getRemotePublicKey();
+}
diff --git a/api/src/main/java/net/azisaba/azipluginmessaging/api/server/PacketSender.java b/api/src/main/java/net/azisaba/azipluginmessaging/api/server/PacketSender.java
index 3a8402a..a7733b9 100644
--- a/api/src/main/java/net/azisaba/azipluginmessaging/api/server/PacketSender.java
+++ b/api/src/main/java/net/azisaba/azipluginmessaging/api/server/PacketSender.java
@@ -8,7 +8,7 @@
 /**
  * Represents an object that can send packet to target.
  */
-public interface PacketSender {
+public interface PacketSender extends Connection {
     /**
      * Attempt to send a packet to the target.
      * @param data the data
@@ -16,15 +16,5 @@ public interface PacketSender {
      */
     boolean sendPacket(byte @NotNull [] data);
 
-    void setEncrypted(boolean encrypted);
-
-    boolean isEncrypted();
-
-    @NotNull
-    KeyPair getKeyPair();
-
-    @NotNull
-    PublicKey getRemotePublicKey();
-
     void setRemotePublicKey(@NotNull PublicKey publicKey);
 }
diff --git a/api/src/main/java/net/azisaba/azipluginmessaging/api/util/Base64Util.java b/api/src/main/java/net/azisaba/azipluginmessaging/api/util/Base64Util.java
index a432cd2..7cb985e 100644
--- a/api/src/main/java/net/azisaba/azipluginmessaging/api/util/Base64Util.java
+++ b/api/src/main/java/net/azisaba/azipluginmessaging/api/util/Base64Util.java
@@ -6,12 +6,22 @@
 import java.util.Base64;
 
 public class Base64Util {
+    /**
+     * Encodes the given byte array to a base64 string.
+     * @param bytes the byte array
+     * @return the base64 string
+     */
     @Contract("_ -> new")
-    public static @NotNull String encode(byte[] bytes) {
+    public static @NotNull String encode(byte @NotNull [] bytes) {
         return Base64.getEncoder().encodeToString(bytes);
     }
 
-    public static byte[] decode(@NotNull String string) {
+    /**
+     * Decodes the given base64 string to a byte array.
+     * @param string the base64 string
+     * @return the byte array
+     */
+    public static byte @NotNull [] decode(@NotNull String string) {
         return Base64.getDecoder().decode(string);
     }
 }
diff --git a/api/src/main/java/net/azisaba/azipluginmessaging/api/util/Constants.java b/api/src/main/java/net/azisaba/azipluginmessaging/api/util/Constants.java
index ce6b734..6822839 100644
--- a/api/src/main/java/net/azisaba/azipluginmessaging/api/util/Constants.java
+++ b/api/src/main/java/net/azisaba/azipluginmessaging/api/util/Constants.java
@@ -3,6 +3,14 @@
 import java.util.Arrays;
 import java.util.List;
 
+/**
+ * @deprecated Deprecated because {@link #SARA_GROUPS} is deprecated.
+ */
+@Deprecated
 public class Constants {
+    /**
+     * @deprecated <code>sara</code> track in LuckPerms should be used instead
+     */
+    @Deprecated
     public static final List<Integer> SARA_GROUPS = Arrays.asList(50000, 20000, 10000, 5000, 2000, 1000, 500, 100);
 }
diff --git a/api/src/main/java/net/azisaba/azipluginmessaging/api/util/EncryptionUtil.java b/api/src/main/java/net/azisaba/azipluginmessaging/api/util/EncryptionUtil.java
index d4afdcc..3619a5d 100644
--- a/api/src/main/java/net/azisaba/azipluginmessaging/api/util/EncryptionUtil.java
+++ b/api/src/main/java/net/azisaba/azipluginmessaging/api/util/EncryptionUtil.java
@@ -10,7 +10,13 @@
 import java.security.PublicKey;
 import java.security.spec.RSAKeyGenParameterSpec;
 
+/**
+ * Represents a utility class for encryption.
+ */
 public class EncryptionUtil {
+    /**
+     * Algorithm to use for encrypting and decrypting packets.
+     */
     public static final String ALGORITHM = "RSA";
 
     /**
@@ -56,11 +62,22 @@ public static byte[] decrypt(byte[] data, @NotNull PrivateKey key) throws Except
         return cipher.doFinal(data);
     }
 
+    /**
+     * Encodes the public key as base64 string.
+     * @param key The key to encode
+     * @return The base64 string
+     */
     @Contract("_ -> new")
     public static @NotNull String encodePublicKey(@NotNull PublicKey key) {
         return Base64Util.encode(key.getEncoded());
     }
 
+    /**
+     * Decodes the base64 string to a public key.
+     * @param key The base64 string
+     * @return The public key
+     * @throws Exception If a public key could not be decoded for any reason
+     */
     @Contract("_ -> new")
     public static @NotNull PublicKey decodePublicKey(@NotNull String key) throws Exception {
         return KeyFactoryUtil.getPublicKey(Base64Util.decode(key));
diff --git a/api/src/main/java/net/azisaba/azipluginmessaging/api/util/KeyFactoryUtil.java b/api/src/main/java/net/azisaba/azipluginmessaging/api/util/KeyFactoryUtil.java
index 341c78f..217c280 100644
--- a/api/src/main/java/net/azisaba/azipluginmessaging/api/util/KeyFactoryUtil.java
+++ b/api/src/main/java/net/azisaba/azipluginmessaging/api/util/KeyFactoryUtil.java
@@ -5,6 +5,12 @@
 import java.security.spec.X509EncodedKeySpec;
 
 public class KeyFactoryUtil {
+    /**
+     * Creates the new instance of PublicKey from given encoded data.
+     * @param encoded the encoded data
+     * @return the PublicKey
+     * @throws Exception If PublicKey could not be created for any reason.
+     */
     public static PublicKey getPublicKey(byte[] encoded) throws Exception {
         X509EncodedKeySpec spec = new X509EncodedKeySpec(encoded);
         KeyFactory kf = KeyFactory.getInstance(EncryptionUtil.ALGORITHM);
diff --git a/api/src/main/java/net/azisaba/azipluginmessaging/api/util/LuckPermsUtil.java b/api/src/main/java/net/azisaba/azipluginmessaging/api/util/LuckPermsUtil.java
index e247102..842fb5f 100644
--- a/api/src/main/java/net/azisaba/azipluginmessaging/api/util/LuckPermsUtil.java
+++ b/api/src/main/java/net/azisaba/azipluginmessaging/api/util/LuckPermsUtil.java
@@ -63,6 +63,13 @@ public static Node findParentNode(@NotNull NodeMap map, @NotNull String group, @
         return map.add(builder.build());
     }
 
+    /**
+     * Finds the prefix nodes set by {@link #setPrefix(NodeMap, String, String)}.
+     * @param map the node map
+     * @param server the server to apply server context to
+     * @return the stream of prefix nodes
+     * @see #findPrefixNode(NodeMap, String, String) findPrefixNode(NodeMap, String, String) for finding a specific prefix node
+     */
     @NotNull
     public static Stream<Node> findPrefixNodes(@NotNull NodeMap map, @Nullable String server) {
         if (server == null) {
@@ -81,6 +88,14 @@ public static Stream<Node> findPrefixNodes(@NotNull NodeMap map, @Nullable Strin
                         node.getContexts().getValues("server").contains(server));
     }
 
+    /**
+     * Find a prefix node set by {@link #setPrefix(NodeMap, String, String)}.
+     * @param map the node map
+     * @param prefix the prefix to find
+     * @param server the server to apply server context to
+     * @return the node, or null if not found
+     * @see #findPrefixNodes(NodeMap, String) findPrefixNodes(NodeMap, String) for finding all prefix nodes under the given server
+     */
     @Nullable
     public static Node findPrefixNode(@NotNull NodeMap map, @NotNull String prefix, @Nullable String server) {
         if (server == null) {
@@ -103,6 +118,13 @@ public static Node findPrefixNode(@NotNull NodeMap map, @NotNull String prefix,
                 .orElse(null);
     }
 
+    /**
+     * Sets the prefix node.
+     * @param map the node map
+     * @param prefix the prefix to set
+     * @param server the server to apply server context to
+     * @return the result of the operation
+     */
     public static @NotNull DataMutateResult setPrefix(@NotNull NodeMap map, @NotNull String prefix, @Nullable String server) {
         PrefixNode.Builder builder = PrefixNode.builder(prefix, 666).value(true);
         if (server != null) builder = builder.withContext("server", server);
diff --git a/api/src/main/java/net/azisaba/azipluginmessaging/api/util/ReflectionUtil.java b/api/src/main/java/net/azisaba/azipluginmessaging/api/util/ReflectionUtil.java
index 1af6876..b42999c 100644
--- a/api/src/main/java/net/azisaba/azipluginmessaging/api/util/ReflectionUtil.java
+++ b/api/src/main/java/net/azisaba/azipluginmessaging/api/util/ReflectionUtil.java
@@ -8,6 +8,13 @@
 public class ReflectionUtil {
     // 1. look for method on superclass
     // 2. look for method on interfaces, then interfaces in interface...
+
+    /**
+     * Finds the method recursively with the given method (uses name and parameter types for finding a method).
+     * @param clazz the base class to look for the method
+     * @param m the method to look for
+     * @return the method if found; null otherwise
+     */
     @Nullable
     public static Method findMethod(@NotNull Class<?> clazz, @NotNull Method m) {
         try {
diff --git a/api/src/main/java/net/azisaba/azipluginmessaging/api/util/TokenUtil.java b/api/src/main/java/net/azisaba/azipluginmessaging/api/util/TokenUtil.java
index 3ec5be1..6be68e2 100644
--- a/api/src/main/java/net/azisaba/azipluginmessaging/api/util/TokenUtil.java
+++ b/api/src/main/java/net/azisaba/azipluginmessaging/api/util/TokenUtil.java
@@ -8,6 +8,10 @@
 public class TokenUtil {
     private static final SecureRandom RANDOM = new SecureRandom();
 
+    /**
+     * Generates a new token.
+     * @return the token
+     */
     public static @NotNull String generateNewToken() {
         return new BigInteger(130, RANDOM).toString(32);
     }
diff --git a/velocity/src/main/java/net/azisaba/azipluginmessaging/velocity/server/ServerConnectionImpl.java b/velocity/src/main/java/net/azisaba/azipluginmessaging/velocity/server/ServerConnectionImpl.java
index 72eefe0..0f77c57 100644
--- a/velocity/src/main/java/net/azisaba/azipluginmessaging/velocity/server/ServerConnectionImpl.java
+++ b/velocity/src/main/java/net/azisaba/azipluginmessaging/velocity/server/ServerConnectionImpl.java
@@ -98,7 +98,7 @@ public void setKeyPair(@NotNull KeyPair keyPair) {
 
     @Override
     public @NotNull PublicKey getRemotePublicKey() {
-        return publicKey;
+        return Objects.requireNonNull(publicKey, "public key is not set");
     }
 
     @Override