.gitignore

@@ -1,3 +1,5 @@
+data.db
+
 .gradle
 build/
 !gradle/wrapper/gradle-wrapper.jar
@@ -39,4 +41,4 @@ bin/
 .vscode/
 
 ### Mac OS ###
-.DS_Store
+.DS_Store

src/main/java/net/pixtaded/crab/Main.java

@@ -7,9 +7,43 @@ import java.util.Scanner;
 
 public class Main {
     public static void main(String[] args) {
-        Scanner scanner = new Scanner(System.in);
+        if (args.length == 0) {
-        chooseMode(scanner);
+            Scanner scanner = new Scanner(System.in);
-        scanner.close();
+            chooseMode(scanner);
+            scanner.close();
+            return;
+        }
+        switch (args[0]) {
+            case "help" -> {
+                System.out.println("crab help - print this message.");
+                System.out.println("crab client <ip> <port> [nick] - connect to a server.");
+                System.out.println("crab server <port> - start a server.");
+            }
+            case "client" -> {
+                CrabClient client;
+                try {
+                    client = new CrabClient(args[1], Integer.parseInt(args[2]), args.length == 4 ? args[3] : null);
+                } catch (NumberFormatException e) {
+                    System.err.println("Port is not a number.");
+                    return;
+                }
+                client.run();
+            }
+            case "server" -> {
+                CrabServer server;
+                try {
+                    server = new CrabServer(Integer.parseInt(args[1]));
+                } catch (NumberFormatException e) {
+                    System.err.println("Port is not a number.");
+                    return;
+                }
+                server.run();
+            }
+            default -> {
+                System.err.println("Unknown argument");
+                return;
+            }
+        }
     }
 
     private static void chooseMode(Scanner scanner) {
@@ -28,4 +62,4 @@ public class Main {
         }
     }
 
-}
+}

src/main/java/net/pixtaded/crab/client/CrabClient.java

@@ -17,15 +17,26 @@ public class CrabClient implements Crab {
     private PrintWriter out;
     private BufferedReader in;
     private int lastBufferLength = 0;
+    private String nickname;
 
     public CrabClient() {
+        this.nickname = "";
+    }
 
+    public CrabClient(String serverAddress, int port, String nickname) {
+        this.serverAddress = serverAddress;
+        this.port = port;
+        if (nickname != null)
+            this.nickname = "<" + nickname + "> ";
+        else
+            this.nickname = "";
     }
 
     @Override
     public void run() {
         try {
-            setup();
+            if (this.serverAddress == null)
+                setup();
             connect();
             communicate();
         } catch (IOException e) {
@@ -54,6 +65,11 @@ public class CrabClient implements Crab {
                 System.out.println("Enter a correct port number: ");
             }
         }
+
+        System.out.print("Enter your nickname (leave empty for no nickname): ");
+        nickname = scanner.nextLine();
+        if (nickname != "")
+            nickname = "<" + nickname + "> ";
     }
 
     private void connect() throws IOException {
@@ -77,7 +93,7 @@ public class CrabClient implements Crab {
                 break;
             }
 
-            if (!message.isEmpty()) sendPacket(MESSAGE, message);
+            if (!message.isEmpty()) sendPacket(MESSAGE, this.nickname + message);
         }
     }
 
@@ -120,4 +136,4 @@ public class CrabClient implements Crab {
         sendPacket(LOGS_SIZE, "");
         sendPacket(LOGS, "");
     }
-}
+}

src/main/java/net/pixtaded/crab/server/CrabServer.java

@@ -18,10 +18,16 @@ public class CrabServer implements Crab {
         this.db = new Database("data.db");
     }
 
+    public CrabServer(int port) {
+        this.db = new Database("data.db");
+        this.port = port;
+    }
+
     @Override
     public void run() {
         try {
-            setup();
+            if (this.port == 0)
+                setup();
             listen();
         } catch (IOException e) {
             if (!isStopped) System.err.println("Error starting server: " + e.getMessage());