To develop an instant messaging server based on the java-language, you can refer to the following books: This book is a classic in the field of Web development, suitable for beginners and experienced developers. The book details the basic knowledge and common techniques of the development of the Web, as well as the development of Web applications based on the java-based technology. It is a good guide for the development of instant messaging servers based on the java-based language. 2 Head First Java: Introduction to object-oriented programming: This is a very popular Head First series of books that also includes chapters on the language. By reading this book, you can better understand the basic concepts and grammar of the Java language. It is also very helpful for the development of instant messaging servers based on the Java language. 3." The Real Combat of Parallel programming in Java ": This book provides a detailed introduction to the basic knowledge and practical skills of parallel programming in Java, including threads, locks, parallel collections, and so on. By reading this book, you can better master the ability of parallel programming in Java and better develop instant messaging servers based on the Java language. 4 Spring Combat: This is a very practical Spring development book, which also includes Spring related content, including Spring MVP, Spring Boot and so on. By reading this book, you can better master Spring technology and better develop instant messaging back-end servers based on the Java language. The above are some books that can be used as reference. Of course, there are many other books that can be used as reference for developers. The specific choice of which book to choose depends on your actual situation and needs.