Java ServerSocketChannel SocketChannel（回調）

Question

我想學習Java。我想實現一個簡單的網絡連接4遊戲以及聊天功能。

我想我的網絡邏輯是非阻塞的，所以經過多番研究後，我發現SocketChannel就是我在重新調整我的需求之後。

還沒有意義的是SocketChannel中缺少CallBack函數..就像在C＃中發現的一樣。

我現在的查詢是：如何將收到的數據傳遞給聊天或遊戲窗體（JFrame）？

一些指導是最受歡迎的。

Answer 1

您需要使用選擇器。首先創建一個選擇接收的事件：

Selector selector = Selector.open() 

然後，你需要註冊與選擇的的ServerSocketChannel：

SelectionKey acceptKey = server.register(selector, SelectionKey.OP_ACCEPT); 

然後，你需要使用選擇，因爲他們進來處理事件（你可以認爲這是該過程的「回調」的一部分：

while(true){ 
    //how many channel keys are available 
    int available = selector.select(); 
    //select is blocking, but should only return if available is >0, this is more of a sanity check 
    if(available == 0) continue; 

    Iterator<SelectionKey> keys = selector.selectedKeys().iterator(); 
    while(keys.hasNext()){ 
    SelectionKey key = keys.next(); 
    keys.remove(); 
    //someone is trying to connect to the server socket 
    if(key.isAcceptable()) doAccept(key); 
    //someone is sending us data 
    else if(key.isReadable()) doRead(key); 
    //we are trying to (and can) send data 
    else if(key.isWritable()) doWrite(key); 
} 

肉將在doAccept（），doRead（），和doWrite（）對於接受鍵選擇鍵將包含INF。 ormation來創建新的Socket。

doAccept(SelectionKey key){ 

//create the new socket 
SocketChannel socket = ((ServerSocketChannel)key.channel()).accept(); 
//make it non-blocking as well 
socket.configureBlocking(false); 

... 
//here you would likely have some code to init your game objects/communication protocol, etc. and generate an identifier object (used below). 
//and be able to find the socket created above 
... 

//Since it is non blocking it needs a selector as well, and we register for both read and write events 
SelectionKey socketKey = socket.register(selector, SelectionKey.OP_READ|SelectionKey.OP_WRITE); 
// so we can identify the events as they come in 
socketKey.attach(someSocketIndentifier); 
} 

最後一行添加了一些對象的鍵，以便從選擇接收的事件可以歸結爲一個連接（例如，它可能是在你的遊戲玩家）。所以現在你可以接受新的連接，你只需要讀寫。

doRead(SelectionKey key){ 
    //here we retrieve the key we attached earlier, so we now what to do/wheer the data is coming from 
    MyIdentifierType myIdentifier = (MyIdentifierType)key.attachment(); 
    //This is then used to get back to the SocketChannel and Read the Data 
    myIdentifier.readTheData(); 
} 

同樣寫

doWrite(SelectionKey key){ 
    //here we retrieve the key we attached earlier, so we now what to do/wheer the data is coming from 
    MyIdentifierType myIdentifier = (MyIdentifierType)key.attachment(); 
    //This is then used to get back to the SocketChannel and Read the Data 
    myIdentifier.getSocketHandler().writePendingData(); 
} 

閱讀是相當簡單的，你只需要創建一個字節緩衝區，然後調用SocketChannels讀取（字節緩衝區）（及其變種或一個），準備好這些數據上該頻道直到它空了。

寫作是有點棘手，你通常會希望緩衝要寫入的數據，直到你收到寫事件：

class MyNetworkClass{ 
    ByteBuffer writeBuffer = ByteBuffer.allocate(1024); 
    SocketChannel commchannel; //from the server accept processing 

    ... 

    public void write(byte[] data){ 
    //here the class writeBuffer object is filled with the data 
    //but it isn't actually sent over the socket 
    ... 
    } 

    public void writePendingData(){ 
    //here actually write the data to the socket 
    commchannel.write(writeBuffer); 
    } 
} 

請注意，您將需要適當的代碼來管理類的緩衝事件變滿了，或者如果緩衝區中的數據沒有全部寫入套接字，則可以在寫掛起方法中適當修改它，以及在此過程中可能拋出的各種異常。希望這有助於你開始。