我正在尝试使用TCP让客户端和服务器相互通信。原始代码运行正常，直到我修改它以添加更多功能。现在，当客户端写入服务器时，服务器似乎永远不会收到任何消息。
以下是客户端和服务器的输出：
客户：欢迎来到Cubby！ 从以下选项中选择：然后列出选项。 然后将该选项写入控制台以进行调试。程序然后要求输入用户名，用户输入一个用户名。然后控制台等待。
服务器：服务器输出它正在等待客户端连接。然后它在客户端连接时显示确认。然后它在那之后什么都不做。它应该向控制台写入客户端发送的选项。
#Client#
import java.math.BigInteger;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.io.*;
import java.net.*;
import java.security.*;
import java.util.*;
public class Client {
private static boolean useSockets = true; // Easy for debugging; turns sockets on/off
public static void main(String[] args) throws Exception {
Socket echoSocket = null; // Client to server socket connection object
PrintWriter out = null; // Out prints to the socket
BufferedReader in = null; // In reads from the socket
int portno = 4444; // The port number of the server we are connecting to
//This assumes the server is also run on a local machine
InetAddress server_name = InetAddress.getLocalHost();
try {
echoSocket = new Socket(server_name, portno);
} catch (UnknownHostException e) {
System.err.println("Don't know about host.");
System.exit(1);
} catch (IOException e) {
System.err.println("Couldn't get I/O for the connection.");
System.exit(1);
}
//Out will write to the socket and in will read from the socket
out = new PrintWriter(echoSocket.getOutputStream());
in = new BufferedReader(new InputStreamReader(echoSocket.getInputStream()));
//Read input from the console
BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
Scanner keyboard = new Scanner(System.in);
//At this point we assume that a TCP connection has been made to the server
//We now ask the user for a username and password.
//If it is the users first time logging in then an account is created.
String choice = welcomeMessage(keyboard);
System.out.println(choice);
if(choice.equals("1")){
out.println(choice);
New_Userlogin(in, out, stdIn);
}
else if (choice.equals("2")){
out.print(choice);
Current_Userlogin(in, out, stdIn);
}
else{
//Exit the program
}
//User has access to Cubby at this point
//Operating System stuff
String os = System.getProperty("os.name").toLowerCase();
String path = System.getProperty("user.home");
if (os.indexOf("win") >= 0) {
path = path+"\\Cubby";
} else if (os.indexOf("mac") >= 0 || os.indexOf("nix") >= 0 || os.indexOf("nux") >= 0) {
path = path+"/Cubby";
} else {
System.out.println("Your OS is not supported");
}
//Create the Cubby folder if it doesn't exist
File f = new File(path);
if(!f.exists()){
f.mkdir();
}
Path dir = Paths.get(path);
WatchDir monitordir = new WatchDir(dir, true);
monitordir.processEvents();
// talking with server handled in WatchDir
//user requests to quit
//sign off from server
if (useSockets)
{
out.close();
in.close();
echoSocket.close();
}
stdIn.close();
}
public static String welcomeMessage(Scanner keyboard){
System.out.println("Welcome to Cubby!");
System.out.println("Select from one of the options below: ");
String choice = "0";
while((!choice.equals("1")) & (!choice.equals("2")) & (!choice.equals("3"))){
System.out.println("1. Create an account: ");
System.out.println("2. Login with an existing account: ");
System.out.println("3. Exit: ");
choice = keyboard.nextLine();
}
return choice;
}
public static void New_Userlogin(BufferedReader in, PrintWriter out, BufferedReader stdIn) throws Exception{
while(true){
System.out.println("Please enter a username: ");
String username = stdIn.readLine();
out.print(username);
int serv_rep = in.read();
if(serv_rep == 0){
System.out.println("Username already taken");
}
else{
System.out.println("Account successfully created");
while(true){
System.out.println("Enter a password: ");
String password = stdIn.readLine();
System.out.println("Confirm Password: ");
String password_check = stdIn.readLine();
if(!password.equals(password_check)){
System.out.println("Passwords did not match. Try again");
}
else{
String hashPass = generateHash(password);
password = "0000000000000000000";
out.print(hashPass);
break;
}
break;
}
}
}
}
public static void Current_Userlogin(BufferedReader in, PrintWriter out, BufferedReader stdIn) throws Exception{
String loginResponse = "invalid";
while (loginResponse != "Good")
{
System.out.println("Please enter your username: ");
String username = stdIn.readLine(); // read in username
System.out.println("Please enter your password:");
String password = stdIn.readLine();
// Hash the password
String hashPass = generateHash(password);
password = "0000000000000000000";
if (useSockets)
{
// Now we need to send the username and hashedpw to the server for validation
out.print(username + "\n" + hashPass);
// Now we need to wait for a valid reply from the server
loginResponse = in.readLine();
}
loginResponse = "Good";
if (loginResponse != "Good")
{
System.out.println("Invalid username and password");
}
}
}
private static String generateHash(String password) throws Exception
{
byte[] hashPass = null;
String hashedPassString = null;
String saltedpw = "!The$Salt^^~" + password;
System.out.println(saltedpw);
MessageDigest sha = MessageDigest.getInstance("SHA-256");
hashPass = sha.digest(saltedpw.getBytes("UTF-8"));
BigInteger number = new BigInteger(1, hashPass);
hashedPassString = number.toString(16);
System.out.println(hashedPassString);
// For security, Java recommends setting the plaintext pw to all 0s after use
saltedpw = "0000000000000000000000000000000000";
password = "0000000000000000000000000000000000";
return hashedPassString;
}
}
#Server#
import java.net.*;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Scanner;
import java.io.*;
public class Server {
//global variable to store the last IP used by the Client
public static int LAST_IP;
public static void main(String[] args) throws IOException, ClassNotFoundException, SQLException {
checkDir();
//First a socket is created on the given port, 4444
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(4444);
} catch (IOException e) {
System.err.println("Could not listen on port: 4444");
System.exit(1);
}
//Then the server does an accept. The server will idle until it
//finds a client to accept it. As it stands, this code will only work
//for one client at a time. There does exist code out there to allow for
//multiple clients if we want to look into that.
Socket clientSocket = null;
try {
System.out.println("Waiting for a client to connect");
clientSocket = serverSocket.accept();
} catch (IOException e) {
System.err.println("Accept failed.");
System.exit(1);
}
System.out.println("Server connected to client");
PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
//The first thing from the client should be a number indicating whether or not
//we need to log the user in or create a new account
//The first is an int indicating new user or an existing user
String choice = null;
// if(in.ready()){
Scanner keyboard = new Scanner(clientSocket.getInputStream());
choice = keyboard.next();
System.out.println(choice);
//}
if(choice.equals("1")){
String username = in.readLine();
createNewUser(username);
}
// else{
// String username = in.readLine();
//String password = in.readLine();
//if(testCredentials(username, password)){
//out.print("Good");
//}
out.close();
in.close();
clientSocket.close();
serverSocket.close();
}
public static void checkDir(){
File f = new File("Users");
//If this is the first time the server is run, there wont be any folder
//If the folder exists, then we leave it alone.
if(!f.exists()){
f.mkdir();
}
}
public static String createNewUser(String name){
//Query the SQL database looking for a username that matches the one a user
//has requested. If there is no username, then return 1. If a match was found
//return 0;
System.out.println("Successfully got to the new User login");
return "0";
}
public static boolean testCredentials(String username, String pass) throws FileNotFoundException, ClassNotFoundException, SQLException
{
}
}
答案 0 :(得分：0)
根据@ asgs的要求，我发布此答案以防其他人偶然发现此问题：
您应该尝试使用out.flush()发送内容后刷新输出流。