Java Nio的简单客户端-服务器示例

Question

Please could you show me a small example in localhost of a client and a server that communicate using java nio? I'd need to understand how it works java nio. For example 1) client requires connection, client connects client sends "Hello i'm a client". 2) Server accepts, server receives message from client, Server responds "hello i'm a server" 3) Client sends "hello server" 4) Server sends "hello client".

I do not need the server to handle multiple clients at a time, what I need to understand is how a connection with multiple messages between client and server happens.

Answer 1

您可以使用以下链接访问您的需求https://www.geeksforgeeks.org/socket-programming-in-java/ https://www.journaldev.com/741/java-socket-programming-server-client

Answer 2

Not really sure why you need to use nio if you are not going to handle multiple connections. I don't see a point in using them.

Alright here goes: Let me know if this works.

Server code:

public class Server {

ServerSocket socket;
Socket listener;

public Server(int port) throws IOException {
    socket = new ServerSocket(port);
}


public void connect() throws IOException{
    listener = socket.accept();
}

public String read() throws IOException{

    byte[] temp = new byte[1024];

    int bytesRead = 0;

    try(InputStream input = listener.getInputStream()){
        bytesRead = input.read(temp);
    }

    return new String(temp,0,bytesRead,"ASCII");
}

public void write(String data) throws IOException{
    byte[] temp = new byte[1024];

    try(OutputStream out = listener.getOutputStream()){
        out.write(data.getBytes());
        out.flush();
    }
}

public void close(){
    socket.close();
}

}

Client code:

public class Client{

Socket client;

InetSocketAddress addr;

public Client(String ip, int port) throws IOException{

    client = new Socket();
    addr = new InetSocketAddress(ip,port);

}


public void connect() throws IOException{
    client.connect(addr);
}

public String read() throws IOException{

    byte[] temp = new byte[1024];

    int bytesRead = 0;

    try(InputStream input = client.getInputStream()){
        bytesRead = input.read(temp);
    }

    return new String(temp,0,bytesRead,"ASCII");
}

public void write(String data) throws IOException{
    byte[] temp = new byte[1024];

    try(OutputStream out = client.getOutputStream()){
        out.write(data.getBytes());
        out.flush();
    }
}

public void close(){
    client.close();
}

}

Now all you have to do is call connect() on the server, then connect() on the client and write and send messages that you want.

Don't forget to call close after you are all done.

Also be aware that you are going to need some mechanism to tell the server and client how long each messages are going to be. Or you can specify an ending character that tells the client/server that the message is over.

One send in the server does not necessarily equal one read in the client and vice versa. You are going to have to figure out what to do.