一个简单的 TCP 回送服务器
我们的 TCP 回送服务器将是一个单独的线程。这是一个简单的开始。它只会以大写的形式回显你发送的任何内容。
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);
}
}
}
现在接受联系。让我们更新 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);
}
}
现在,如果你可以打开 telnet 并尝试连接,你将看到欢迎消息。
你必须连接指定的端口和 IP 地址。
你应该看到与此类似的结果:
Welcome!
Connection to host lost.
好吧,连接丢失了,因为我们终止了它。有时我们必须编写自己的 TCP 客户端。在这种情况下,我们需要客户端请求来自用户的输入并通过网络发送,接收大写输入。
如果服务器首先发送数据,则客户端必须首先读取数据。
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);
}
}
}
}
现在更新服务器
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();
现在运行服务器和客户端,你应该有一个类似于此的输出
Welcome!
>