Java客户端/服务器应用程序与套接字？ [英] Java client/server application with sockets?
问题描述
我正在编写一个将被另一种语言（matlab）调用的java包。如果我的matlab过程结束，我想让Java进程继续运行。每当matlab再次启动时，它应该能够与现有运行的进程通信。所以我认为我需要让Java应用程序通过客户端/服务器模型中的套接字进行通信。我设想一个简单的函数集：
I'm writing a java package that will be called by another language (matlab). If my matlab process ends, I want the Java process to keep running. Whenever matlab starts again, it should be able to communicate with the existing running process. So I think I need to have the Java application communicating through sockets in a client/server model. I envision having a simple set of functions:
- startServer（host，port）
- runCommand server，command ...）
- stopServer（host，port）
做这样的事情之前。我是以正确的方式思考它，还是有一种更容易的方法来构建一个可以独立于其父进程运行的应用程序？什么是最好的现代方式这样做（例如有什么好的Apache包）？任何人都可以提供一个简单的演示或指向一个关于通过套接字与流程通信的教程。
I have never done anything like this before. Am I thinking about it in the right way, or is there an easier way of building an application that can run independently of it's parent's process? What's the best modern way of doing this (e.g. are there any good Apache packages)? Can anyone provide a simple demo or point me to a tutorial on communicating with a process through sockets?
能够实例化一个java对象并在其内部运行java代码。因此，matlab中的startServer（）函数将运行Java代码，该代码将检查Java进程是否已在该端口上运行，如果没有，则启动服务器进程。
For some clarification, matlab is able to instantiate a java object and run java code within itself. So the startServer() function in matlab would run java code that will check if a java process is already running on that port and if not, start the server process.
我并不是用任何方式使用套接字（如果它不明显，我主要是一个matlab开发人员），所以如果有一些更容易，我所有的。我只需要能够独立运行matlab，但有matlab控制这些进程（通过java）。
I'm not tied to using sockets by any means (in case it isn't obvious, I'm mostly a matlab developer), so if there's something easier, I'm all for it. I just need to be able to run things independently of matlab, but have matlab control those processes (through java).
推荐答案
服务器侦听连接。当客户端建立连接时。客户端可以发送数据。在当前示例中，客户端发送消息Hi我的服务器。要终止连接，客户端将发送消息bye。然后服务器发送消息再见。最后，连接结束，服务器等待另一个连接。这两个程序应该在同一台机器上运行。然而，如果你想在两个不同的机器上运行它们，你可以简单地改变地址localhost由你将运行服务器的机器的IP地址。
The server listens for a connection. When a connection is established by a client. The client can send data. In the current example the client sends the message "Hi my server". To terminate the connection, the client sends the message "bye". Then the server sends the message "bye" too. Finally the connection is ended and the server waits for an other connection. The two programs should be running in the same machine. however if you want to run them in two different machines, you may simply change the address "localhost" by the IP address of the machine where you will run the server.
服务器
import java.io.*;
import java.net.*;
public class Provider{
ServerSocket providerSocket;
Socket connection = null;
ObjectOutputStream out;
ObjectInputStream in;
String message;
Provider(){}
void run()
{
try{
//1. creating a server socket
providerSocket = new ServerSocket(2004, 10);
//2. Wait for connection
System.out.println("Waiting for connection");
connection = providerSocket.accept();
System.out.println("Connection received from " + connection.getInetAddress().getHostName());
//3. get Input and Output streams
out = new ObjectOutputStream(connection.getOutputStream());
out.flush();
in = new ObjectInputStream(connection.getInputStream());
sendMessage("Connection successful");
//4. The two parts communicate via the input and output streams
do{
try{
message = (String)in.readObject();
System.out.println("client>" + message);
if (message.equals("bye"))
sendMessage("bye");
}
catch(ClassNotFoundException classnot){
System.err.println("Data received in unknown format");
}
}while(!message.equals("bye"));
}
catch(IOException ioException){
ioException.printStackTrace();
}
finally{
//4: Closing connection
try{
in.close();
out.close();
providerSocket.close();
}
catch(IOException ioException){
ioException.printStackTrace();
}
}
}
void sendMessage(String msg)
{
try{
out.writeObject(msg);
out.flush();
System.out.println("server>" + msg);
}
catch(IOException ioException){
ioException.printStackTrace();
}
}
public static void main(String args[])
{
Provider server = new Provider();
while(true){
server.run();
}
}
}
客户
import java.io.*;
import java.net.*;
public class Requester{
Socket requestSocket;
ObjectOutputStream out;
ObjectInputStream in;
String message;
Requester(){}
void run()
{
try{
//1. creating a socket to connect to the server
requestSocket = new Socket("localhost", 2004);
System.out.println("Connected to localhost in port 2004");
//2. get Input and Output streams
out = new ObjectOutputStream(requestSocket.getOutputStream());
out.flush();
in = new ObjectInputStream(requestSocket.getInputStream());
//3: Communicating with the server
do{
try{
message = (String)in.readObject();
System.out.println("server>" + message);
sendMessage("Hi my server");
message = "bye";
sendMessage(message);
}
catch(ClassNotFoundException classNot){
System.err.println("data received in unknown format");
}
}while(!message.equals("bye"));
}
catch(UnknownHostException unknownHost){
System.err.println("You are trying to connect to an unknown host!");
}
catch(IOException ioException){
ioException.printStackTrace();
}
finally{
//4: Closing connection
try{
in.close();
out.close();
requestSocket.close();
}
catch(IOException ioException){
ioException.printStackTrace();
}
}
}
void sendMessage(String msg)
{
try{
out.writeObject(msg);
out.flush();
System.out.println("client>" + msg);
}
catch(IOException ioException){
ioException.printStackTrace();
}
}
public static void main(String args[])
{
Requester client = new Requester();
client.run();
}
}
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