[英]Java: Simple Client Server message exchange not working
我是Java的新手,昨天才剛開始。 我寫了一個非常簡單的客戶端服務器Java代碼。 客戶端向服務器發送消息。 服務器應顯示該消息。 並且服務器應在收到消息后向客戶端發送消息。 客戶端應顯示服務器發送的消息。
服務器代碼,
import java.io.InputStreamReader;
import java.io.BufferedReader;
import java.io.OutputStreamWriter;
import java.io.BufferedWriter;
import java.net.Socket;
import java.net.ServerSocket;
public class CustomServer{
public static void main(String[] args){
final int SERVER_PORT_NUMBER = 8081;
try{
ServerSocket serverObj = new ServerSocket(SERVER_PORT_NUMBER);
Socket clientSocketObj = serverObj.accept();
BufferedReader clientInputStream = new BufferedReader(new InputStreamReader(clientSocketObj.getInputStream()));
BufferedWriter clientOutputStream = new BufferedWriter(new OutputStreamWriter(clientSocketObj.getOutputStream()));
if(clientSocketObj != null){
System.out.println("Client Connected to Server!");
// Recieve Message from Client
System.out.println("MESSAGE FROM CLIENT");
System.out.println(clientInputStream.readLine());
// Send Message to Client
clientOutputStream.write("SERVER: Hello Client!");
// Close Streams
clientOutputStream.close();
clientInputStream.close();
}
serverObj.close();
}
catch(Exception e){
System.out.println(e);
}
}
}
客戶,
import java.io.BufferedWriter;
import java.io.OutputStreamWriter;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.Socket;
public class CustomClient{
public static void main(String[] args){
final String HOST_NAME = "127.0.0.1";
final int SERVER_PORT_NUMBER = 8081;
try{
Socket clientSocket = new Socket(HOST_NAME, SERVER_PORT_NUMBER);
BufferedWriter clientOutputStream = new BufferedWriter(new OutputStreamWriter(clientSocket.getOutputStream()));
BufferedReader clientInputStream = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
System.out.println("Connecting....");
if(clientSocket != null){
System.out.println("Connected to Server!");
// Send message to Server
clientOutputStream.write("CLIENT: HELLO SERVER");
// Recieve message from Server
System.out.println("MESSAGE FROM SERVER");
System.out.println(clientInputStream.readLine());
// Close Streams
clientInputStream.close();
clientOutputStream.close();
}
clientSocket.close();
}
catch(Exception e){
System.out.println(e);
}
}
}
服務器或客戶端均未收到該消息。 卡在某個循環中。 有人知道為什么嗎?
首先讀取BufferedReader
的JavaDocs ,該狀態為
讀取一行文本。 一行被認為由換行符('\\ n'),回車符('\\ r')或回車符后立即換行符中的任何一個終止
BufferedWriter#write
沒有發送此消息,因此閱讀器仍在等待。
一個簡單的解決方案可能是在write
后使用BufferedWriter#newLine
而且,當您完成對緩沖區的寫操作時,請不要忘記刷新它!
您可能還想看一看try-with-resources ,它將提供更好的資源管理解決方案
CustomClient
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.Socket;
public class CustomClient {
public static void main(String[] args) {
final String HOST_NAME = "127.0.0.1";
final int SERVER_PORT_NUMBER = 8081;
try (Socket clientSocket = new Socket(HOST_NAME, SERVER_PORT_NUMBER)) {
try (BufferedWriter clientOutputStream = new BufferedWriter(new OutputStreamWriter(clientSocket.getOutputStream()));
BufferedReader clientInputStream = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()))) {
System.out.println("Connecting....");
System.out.println("Connected to Server!");
// Send message to Server
clientOutputStream.write("CLIENT: HELLO SERVER");
clientOutputStream.newLine();
clientOutputStream.flush();
// Recieve message from Server
System.out.println("MESSAGE FROM SERVER");
System.out.println(clientInputStream.readLine());
}
} catch (Exception e) {
System.out.println(e);
}
}
}
CustomServer
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.ServerSocket;
import java.net.Socket;
public class CustomServer {
public static void main(String[] args) {
final int SERVER_PORT_NUMBER = 8081;
try (ServerSocket serverObj = new ServerSocket(SERVER_PORT_NUMBER)) {
try (Socket clientSocketObj = serverObj.accept()) {
try (BufferedReader clientInputStream = new BufferedReader(new InputStreamReader(clientSocketObj.getInputStream()));
BufferedWriter clientOutputStream = new BufferedWriter(new OutputStreamWriter(clientSocketObj.getOutputStream()))) {
System.out.println("Client Connected to Server!");
// Recieve Message from Client
System.out.println("MESSAGE FROM CLIENT");
System.out.println(clientInputStream.readLine());
// Send Message to Client
clientOutputStream.write("SERVER: Hello Client!");
clientOutputStream.newLine();
clientOutputStream.flush();
}
}
} catch (Exception e) {
System.out.println(e);
}
}
}
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