MCP Troubleshooter

Implementation Reference

• src/index.ts:525-555 (handler)

  The handler function tests port availability by attempting to create and listen on a temporary HTTP server on the given port. If it listens successfully, the port is available; if EADDRINUSE error, it's in use; other errors are reported.

  async ({ port }) => {
    return new Promise((resolve) => {
      const server = createServer();
      
      server.once('error', (err) => {
        if (err.code === 'EADDRINUSE') {
          resolve({
            content: [{ 
              type: "text", 
              text: `Port ${port} is already in use. This might indicate another server is running on this port.` 
            }]
          });
        } else {
          resolve({
            isError: true,
            content: [{ type: "text", text: `Error testing port ${port}: ${err.message}` }]
          });
        }
        server.close();
      });
      
      server.once('listening', () => {
        resolve({
          content: [{ type: "text", text: `Port ${port} is available.` }]
        });
        server.close();
      });
      
      server.listen(port, '127.0.0.1');
    });
  }

• src/index.ts:522-524 (schema)

  Zod schema defining the input parameter 'port' as an integer between 1 and 65535.

  {
    port: z.number().int().min(1).max(65535).describe("Port number to test")
  },

• src/index.ts:520-556 (registration)

  Registers the tool 'test-port-availability' on the MCP server, including schema and inline handler implementation.

  server.tool(
    "test-port-availability",
    {
      port: z.number().int().min(1).max(65535).describe("Port number to test")
    },
    async ({ port }) => {
      return new Promise((resolve) => {
        const server = createServer();
        
        server.once('error', (err) => {
          if (err.code === 'EADDRINUSE') {
            resolve({
              content: [{ 
                type: "text", 
                text: `Port ${port} is already in use. This might indicate another server is running on this port.` 
              }]
            });
          } else {
            resolve({
              isError: true,
              content: [{ type: "text", text: `Error testing port ${port}: ${err.message}` }]
            });
          }
          server.close();
        });
        
        server.once('listening', () => {
          resolve({
            content: [{ type: "text", text: `Port ${port} is available.` }]
          });
          server.close();
        });
        
        server.listen(port, '127.0.0.1');
      });
    }
  );