diff --git a/main.py b/main.py
index 92d705b4d..090971188 100644
--- a/main.py
+++ b/main.py
@@ -2,6 +2,7 @@ import comfy.options
 comfy.options.enable_args_parsing()
 
 import os
+import socket
 import importlib.util
 import folder_paths
 import time
@@ -383,6 +384,32 @@ def start_comfyui(asyncio_loop=None):
     if not asyncio_loop:
         asyncio_loop = asyncio.new_event_loop()
         asyncio.set_event_loop(asyncio_loop)
+    
+    # Check if server port is available before loading custom nodes
+    server_host = args.listen if args.listen else "0.0.0.0"
+    server_port = args.port if args.port else 8188
+    
+    # Check port availability
+    try:
+        with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
+            sock.settimeout(1)
+            result = sock.connect_ex((server_host, server_port))
+            if result == 0:
+                logging.error(f"\n{'='*60}")
+                logging.error(f"PORT CONFLICT DETECTED")
+                logging.error(f"{'='*60}")
+                logging.error(f"Port {server_port} on {server_host} is already in use.")
+                logging.error(f"Please either:")
+                logging.error(f"  1. Stop the other process using port {server_port}")
+                logging.error(f"  2. Start ComfyUI on a different port using: --port <PORT>")
+                logging.error(f"{'='*60}\n")
+                sys.exit(1)
+            else:
+                logging.info(f"Port {server_port} is available.")
+    except socket.error as e:
+        logging.error(f"Error checking port {server_port}: {e}")
+        sys.exit(1)
+    
     prompt_server = server.PromptServer(asyncio_loop)
 
     if args.enable_manager and not args.disable_manager_ui:
diff --git a/port_check.py b/port_check.py
new file mode 100644
index 000000000..f1cf053bb
--- /dev/null
+++ b/port_check.py
@@ -0,0 +1,67 @@
+"""
+Port check utility for ComfyUI
+Checks if the server port is available before starting
+to avoid port conflicts after custom nodes load
+"""
+
+import socket
+import sys
+import logging
+
+
+def check_port_available(host, port, timeout=1):
+    """
+    Check if a port is available for binding.
+    
+    Args:
+        host: Host address to check
+        port: Port number to check
+        timeout: Connection timeout in seconds
+        
+    Returns:
+        True if port is available, False otherwise
+    """
+    try:
+        with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
+            sock.settimeout(timeout)
+            result = sock.connect_ex((host, port))
+            if result == 0:
+                # Port is in use
+                return False
+            else:
+                # Port is available
+                return True
+    except socket.error as e:
+        logging.error(f"Error checking port {port}: {e}")
+        return False
+
+
+def check_server_port(host, port):
+    """
+    Check if the server port is available and exit if not.
+    This should be called early in the startup process.
+    
+    Args:
+        host: Host address
+        port: Port number
+        
+    Raises:
+        SystemExit: If port is not available
+    """
+    if not check_port_available(host, port):
+        logging.error(f"\n{'='*60}")
+        logging.error(f"PORT CONFLICT DETECTED")
+        logging.error(f"{'='*60}")
+        logging.error(f"Port {port} on {host} is already in use.")
+        logging.error(f"Please either:")
+        logging.error(f"  1. Stop the other process using port {port}")
+        logging.error(f"  2. Start ComfyUI on a different port using: --port <PORT>")
+        logging.error(f"{'='*60}\n")
+        sys.exit(1)
+    else:
+        logging.info(f"Port {port} is available.")
+
+
+if __name__ == "__main__":
+    # Simple test
+    print(f"Checking port 8188: {check_port_available('127.0.0.1', 8188)}")
diff --git a/test_port_check.py b/test_port_check.py
new file mode 100644
index 000000000..d68595c6d
--- /dev/null
+++ b/test_port_check.py
@@ -0,0 +1,61 @@
+"""
+Test for port check functionality in ComfyUI
+"""
+
+import socket
+import threading
+import time
+import sys
+sys.path.insert(0, '/tmp/comfyui-port-check')
+
+from port_check import check_port_available, check_server_port
+
+
+def test_port_available():
+    """Test that an available port returns True"""
+    # Find an available port
+    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
+        s.bind(('127.0.0.1', 0))
+        port = s.getsockname()[1]
+    
+    # Check that it's available
+    result = check_port_available('127.0.0.1', port)
+    assert result == True, f"Port {port} should be available"
+    print(f"✅ Port {port} is available (as expected)")
+
+
+def test_port_in_use():
+    """Test that an in-use port returns False"""
+    # Create a socket and bind it
+    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    sock.bind(('127.0.0.1', 0))
+    port = sock.getsockname()[1]
+    sock.listen(1)
+    
+    try:
+        # Check that it's NOT available
+        result = check_port_available('127.0.0.1', port)
+        assert result == False, f"Port {port} should NOT be available"
+        print(f"✅ Port {port} is correctly detected as in-use")
+    finally:
+        sock.close()
+
+
+def test_port_check_timeout():
+    """Test that port check handles timeout gracefully"""
+    # This should not hang
+    result = check_port_available('192.0.2.1', 12345, timeout=0.1)
+    # Result may vary depending on network, but should not hang
+    print(f"✅ Port check completed without hanging")
+
+
+if __name__ == "__main__":
+    print("Testing port check functionality...")
+    print()
+    
+    test_port_available()
+    test_port_in_use()
+    test_port_check_timeout()
+    
+    print()
+    print("All tests passed! ✅")