一個簡單的 TCP 回送伺服器
我們的 TCP 回送伺服器將是一個單獨的執行緒。這是一個簡單的開始。它只會以大寫的形式回顯你傳送的任何內容。
public class CAPECHOServer extends Thread{
// This class implements server sockets. A server socket waits for requests to come
// in over the network only when it is allowed through the local firewall
ServerSocket serverSocket;
public CAPECHOServer(int port, int timeout){
try {
// Create a new Server on specified port.
serverSocket = new ServerSocket(port);
// SoTimeout is basiacally the socket timeout.
// timeout is the time until socket timeout in milliseconds
serverSocket.setSoTimeout(timeout);
} catch (IOException ex) {
Logger.getLogger(CAPECHOServer.class.getName()).log(Level.SEVERE, null, ex);
}
}
@Override
public void run(){
try {
// We want the server to continuously accept connections
while(!Thread.interrupted()){
}
// Close the server once done.
serverSocket.close();
} catch (IOException ex) {
Logger.getLogger(CAPECHOServer.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
現在接受聯絡。讓我們更新 run 方法。
@Override
public void run(){
while(!Thread.interrupted()){
try {
// Log with the port number and machine ip
Logger.getLogger((this.getClass().getName())).log(Level.INFO, "Listening for Clients at {0} on {1}", new Object[]{serverSocket.getLocalPort(), InetAddress.getLocalHost().getHostAddress()});
Socket client = serverSocket.accept(); // Accept client conncetion
// Now get DataInputStream and DataOutputStreams
DataInputStream istream = new DataInputStream(client.getInputStream()); // From client's input stream
DataOutputStream ostream = new DataOutputStream(client.getOutputStream());
// Important Note
/*
The server's input is the client's output
The client's input is the server's output
*/
// Send a welcome message
ostream.writeUTF("Welcome!");
// Close the connection
istream.close();
ostream.close();
client.close();
} catch (IOException ex) {
Logger.getLogger(CAPECHOServer.class.getName()).log(Level.SEVERE, null, ex);
}
}
// Close the server once done
try {
serverSocket.close();
} catch (IOException ex) {
Logger.getLogger(CAPECHOServer.class.getName()).log(Level.SEVERE, null, ex);
}
}
現在,如果你可以開啟 telnet 並嘗試連線,你將看到歡迎訊息。
你必須連線指定的埠和 IP 地址。
你應該看到與此類似的結果:
Welcome!
Connection to host lost.
好吧,連線丟失了,因為我們終止了它。有時我們必須編寫自己的 TCP 客戶端。在這種情況下,我們需要客戶端請求來自使用者的輸入並通過網路傳送,接收大寫輸入。
如果伺服器首先傳送資料,則客戶端必須首先讀取資料。
public class CAPECHOClient extends Thread{
Socket server;
Scanner key; // Scanner for input
public CAPECHOClient(String ip, int port){
try {
server = new Socket(ip, port);
key = new Scanner(System.in);
} catch (IOException ex) {
Logger.getLogger(CAPECHOClient.class.getName()).log(Level.SEVERE, null, ex);
}
}
@Override
public void run(){
DataInputStream istream = null;
DataOutputStream ostream = null;
try {
istream = new DataInputStream(server.getInputStream()); // Familiar lines
ostream = new DataOutputStream(server.getOutputStream());
System.out.println(istream.readUTF()); // Print what the server sends
System.out.print(">");
String tosend = key.nextLine();
ostream.writeUTF(tosend); // Send whatever the user typed to the server
System.out.println(istream.readUTF()); // Finally read what the server sends before exiting.
} catch (IOException ex) {
Logger.getLogger(CAPECHOClient.class.getName()).log(Level.SEVERE, null, ex);
} finally {
try {
istream.close();
ostream.close();
server.close();
} catch (IOException ex) {
Logger.getLogger(CAPECHOClient.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
}
現在更新伺服器
ostream.writeUTF("Welcome!");
String inString = istream.readUTF(); // Read what the user sent
String outString = inString.toUpperCase(); // Change it to caps
ostream.writeUTF(outString);
// Close the connection
istream.close();
現在執行伺服器和客戶端,你應該有一個類似於此的輸出
Welcome!
>