diff --git a/src/Channel.ts b/src/Channel.ts
index b6febb9..c5e9b2e 100644
--- a/src/Channel.ts
+++ b/src/Channel.ts
@@ -3,6 +3,7 @@ import { MatrixUser } from "./MatrixUser.js";
 import { IRCUser } from "./IRCUser.js";
 import { Client } from "./Client.js";
 import numerics from "./numerics.js";
+import { IRCMessage } from "./Message.js";
 
 export class Channel {
     public name: string
@@ -46,7 +47,9 @@ export class Channel {
         if (!newName || newName === this.name)
             return;
         const oldName = this.name;
+        this.server.ircChannels.delete(oldName);
         this.name = newName;
+        this.server.ircChannels.set(newName, this);
         this.ircUsers.forEach((user, username) => {
             user.getClients().forEach(client => {
                 if (client.enabledCaps.has("draft/channel-rename")) {
@@ -136,7 +139,11 @@ export class Channel {
             ]
             client.sendMessage(client.server.name, '352', userParams, passedTags);
         }
-        client.sendMessage(client.server.name, '315', [this.name], passedTags);
+        client.sendMessage(client.server.name, '315', [client.user.nick, this.name, "End of /WHO"], passedTags);
+    }
+
+    handleModeChange(client: Client, message: IRCMessage) {
+
     }
 
     routeMatrixEvent(event: any) {
diff --git a/src/Client.ts b/src/Client.ts
index d6da89f..a5a0528 100644
--- a/src/Client.ts
+++ b/src/Client.ts
@@ -49,6 +49,56 @@ export class Client {
         });
     }
 
+    checkIfRegistered(passedTags: Map<string, string> = new Map()) {
+        if (this.user === null)
+            this.sendMessage(this.server.name, "451", [this.localNick, "You have not registered"], passedTags);
+
+        return this.user !== null;
+    }
+
+    getMatrixUserFromNick(targetNick: string, passedTags: Map<string, string> = new Map()) {
+        if (!this.user) return false;
+        const targetMxid = this.server.nickToMxid.get(targetNick);
+        if (!targetMxid) {
+            this.sendMessage(this.server.name, "401", [this.user.nick, targetNick, "No such nick"], passedTags);
+            return false;
+        }
+        const target = this.server.matrixUsers.get(targetMxid);
+        if (!target) {
+            this.sendMessage(this.server.name, "401", [this.user.nick, targetNick, "No such nick"], passedTags);
+            return false;
+        }
+        return target;
+    }
+
+    getChannel(channel: string, passedTags: Map<string, string> = new Map()) {
+        if (!this.user) return false;
+        const targetChannel = this.server.ircChannels.get(channel);
+        if (!targetChannel) {
+            this.sendMessage(this.server.name, "403", [this.user.nick, channel, "No such channel"], passedTags);
+            return false;
+        }
+        return targetChannel;
+    }
+
+    checkIfInChannel(channel: Channel, passedTags: Map<string, string> = new Map()) {
+        if (!this.user) return false;
+        if (!channel.ircUsers.has(this.user.nick)) {
+            this.sendMessage(this.server.name, "442", [this.user.nick, "You're not on that channel"], passedTags);
+            return false;
+        }
+        return true;
+    }
+
+    checkMinParams(message: IRCMessage, neededNumber: number) {
+        if (!this.user) return false;
+        if (message.params.length < neededNumber) {
+            this.sendMessage(this.server.name, "461", [this.user.nick, message.command, "Not enough parameters"], message.tags);
+            return false;
+        }
+        return true;
+    }
+
     routeMessage(data: string) {
         const message = parseIRCMessage(data);
         switch (message.command.toUpperCase()) {
@@ -61,47 +111,80 @@ export class Client {
                 break;
             }
             case 'INVITE': {
-                const targetUser = this.server.getOrCreateMatrixUser(message.params[0])
-                const targetChannel = this.server.ircChannels.get(message.params[1]);
+                if (!this.checkIfRegistered(message.tags) || !this.checkMinParams(message, 2))
+                    return;
+                const targetUser = this.getMatrixUserFromNick(message.params[0], message.tags);
+                const targetChannel = this.getChannel(message.params[1], message.tags);
+                if (!this.user || !targetUser || !targetChannel) return;
+                if (!this.checkIfInChannel(targetChannel, message.tags)) return;
+                if (targetChannel.matrixUsers.has(targetUser.nick)) {
+                    this.sendMessage(this.server.name, "443", [this.user.nick, targetUser.nick, "is already on channel"], message.tags);
+                    return;
+                }
                 const reason = (message.params.length === 3) ? message.params[2] : "";
-                if (this.user && targetChannel && targetChannel.ircUsers.get(this.user.nick))
-                    this.user.inviteMatrixUser(this, targetChannel, targetUser, reason, message.tags);
+                this.user.inviteMatrixUser(this, targetChannel, targetUser, reason, message.tags);
                 break;
             }
             case 'KICK': {
-                const targetChannel = this.server.ircChannels.get(message.params[0]);
-                const targetMxid = this.server.nickToMxid.get(message.params[1]);
-                if (!targetMxid)
+                if (!this.checkIfRegistered(message.tags) || !this.checkMinParams(message, 2))
                     return;
-                console.log(targetMxid);
+                const targetChannel = this.getChannel(message.params[0], message.tags);
+                const targetUser = this.getMatrixUserFromNick(message.params[1], message.tags);
+                if (!this.user || !targetUser || !targetChannel) return;
+                if (!this.checkIfInChannel(targetChannel, message.tags)) return;
+                if (!targetChannel.matrixUsers.has(targetUser.nick)) {
+                    this.sendMessage(this.server.name, "441", [this.user.nick, targetUser.nick, targetChannel.name, "They aren't on that channel"], message.tags);
+                    return;
+                }
                 const reason = (message.params.length === 3) ? message.params[2] : "";
-                if (this.user && targetChannel && targetChannel.ircUsers.get(this.user.nick))
-                    this.user.kickMatrixUser(this, targetChannel, targetMxid, reason, message.tags);
+                this.user.kickMatrixUser(this, targetChannel, targetUser.mxid, reason, message.tags);
                 break;
             }
             case 'MODE': {
+                if (!this.checkIfRegistered(message.tags) || !this.checkMinParams(message, 1) || !this.user)
+                    return;
                 const targetChannel = this.server.ircChannels.get(message.params[0]);
-                if (this.user && targetChannel && targetChannel.ircUsers.get(this.user.nick))
+                if (!targetChannel) {
+                    if (message.params[0] !== this.user.nick) {
+                        this.sendMessage(this.server.name, "502", [this.user.nick, "Can't view mode for other users"], message.tags);
+                        return;
+                    }
+                    this.sendMessage(this.server.name, "221", [this.user.nick, "+i"], message.tags);
+                    return;
+                }
+                if (!this.checkIfInChannel(targetChannel, message.tags)) return;
+                if (message.params.length === 1)
                     targetChannel.sendMode(this, message.tags);
+                else
+                    targetChannel.handleModeChange(this, message);
                 break;
             }
             case 'NAMES': {
-                const targetChannel = this.server.ircChannels.get(message.params[0]);
-                if (this.user && targetChannel && targetChannel.ircUsers.get(this.user.nick))
-                    targetChannel.sendNames(this, message.tags);
+                if (!this.checkIfRegistered(message.tags) || !this.checkMinParams(message, 1))
+                    return;
+                const targetChannel = this.getChannel(message.params[0], message.tags);
+                if (!this.user || !targetChannel) return;
+                if (!this.checkIfInChannel(targetChannel, message.tags)) return;
+                targetChannel.sendNames(this, message.tags);
                 break;
             }
             case 'NOTICE': {
-                if (this.user) {
-                    this.user.sendMessageToMatrix(message, this);
-                }
+                if (!this.checkIfRegistered(message.tags) || !this.checkMinParams(message, 2))
+                    return;
+                const targetChannel = this.getChannel(message.params[0], message.tags);
+                if (!this.user || !targetChannel) return;
+                if (!this.checkIfInChannel(targetChannel, message.tags)) return;
+                this.user.sendMessageToMatrix(message, this);
                 break;
             }
             case 'PART': {
-                const targetChannel = this.server.ircChannels.get(message.params[0]);
+                if (!this.checkIfRegistered(message.tags) || !this.checkMinParams(message, 1))
+                    return;
+                const targetChannel = this.getChannel(message.params[0], message.tags);
+                if (!this.user || !targetChannel) return;
+                if (!this.checkIfInChannel(targetChannel, message.tags)) return;
                 const reason = (message.params.length === 2) ? message.params[1] : ""; 
-                if (this.user && targetChannel && targetChannel.ircUsers.get(this.user.nick))
-                    this.user.partMatrixRoom(this, targetChannel, reason, message.tags);
+                this.user.partMatrixRoom(this, targetChannel, reason, message.tags);
                 break;
             }
             case 'PING': {
@@ -109,21 +192,29 @@ export class Client {
                 break;
             }
             case 'PRIVMSG': {
-                if (this.user) {
-                    this.user.sendMessageToMatrix(message, this);
-                }
+                if (!this.checkIfRegistered(message.tags) || !this.checkMinParams(message, 2))
+                    return;
+                const targetChannel = this.getChannel(message.params[0], message.tags);
+                if (!this.user || !targetChannel) return;
+                if (!this.checkIfInChannel(targetChannel, message.tags)) return;
+                this.user.sendMessageToMatrix(message, this);
                 break;
             }
             case 'TAGMSG': {
-                if (this.user) {
-                    this.user.sendTagToMatrix(message, this);
-                }
+                if (!this.checkIfRegistered(message.tags) || !this.checkMinParams(message, 1))
+                    return;
+                const targetChannel = this.getChannel(message.params[0], message.tags);
+                if (!this.user || !targetChannel) return;
+                if (!this.checkIfInChannel(targetChannel, message.tags)) return;
+                this.user.sendTagToMatrix(message, this);
                 break;
             }
             case 'TOPIC': {
-                const targetChannel = this.server.ircChannels.get(message.params[0]);
-                if (!this.user || !targetChannel || !targetChannel.ircUsers.get(this.user.nick))
-                    break;
+                if (!this.checkIfRegistered(message.tags) || !this.checkMinParams(message, 1))
+                    return;
+                const targetChannel = this.getChannel(message.params[0], message.tags);
+                if (!this.user || !targetChannel) return;
+                if (!this.checkIfInChannel(targetChannel, message.tags)) return;
                 if (message.params.length === 1) {
                     targetChannel.sendTopic(this, message.tags);
                     break;
@@ -133,9 +224,12 @@ export class Client {
                 break;
             }
             case 'WHO': {
-                const targetChannel = this.server.ircChannels.get(message.params[0]);
-                if (this.user && targetChannel && targetChannel.ircUsers.get(this.user.nick))
-                    targetChannel.sendWho(this, message.tags);
+                if (!this.checkIfRegistered(message.tags) || !this.checkMinParams(message, 1))
+                    return;
+                const targetChannel = this.getChannel(message.params[0], message.tags);
+                if (!this.user || !targetChannel) return;
+                if (!this.checkIfInChannel(targetChannel, message.tags)) return;
+                targetChannel.sendWho(this, message.tags);
                 break;
             }
         }
diff --git a/src/numerics.ts b/src/numerics.ts
index 3ee6030..628a8bc 100644
--- a/src/numerics.ts
+++ b/src/numerics.ts
@@ -36,7 +36,7 @@ const numerics = {
         return [nick, "End of MOTD"]
     },
     "433": (nick: string, otherNick: string) => {
-        return [nick, otherNick, "You can't change nicks on IRC yet"]
+        return [nick, otherNick, "Nickname is already in use"]
     },
     "900": (mask: string, nick: string) => {
         return [nick, mask, `You are now logged in as ${nick}`]