我在使用 TCP/IP 的 Java 中实现了以下算法：
-Client request a file
-Server checks if the file exists
- if do: send contents of the file to the client
- if not: send "file not found" msg to the client
现在我在使用 UDP 数据包实现它时遇到了麻烦。这是我的代码：
客户：
package br.com.redes.client;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;
import br.com.redes.configuration.CommonKeys;
public class TCPClient {
public static void exibirCabecalho(){
System.out.println("-------------------------");
System.out.println("TCP CLIENT");
System.out.println("-------------------------");
}
public static void main(String[] args) throws IOException {
TCPClient.exibirCabecalho();
Socket echoSocket = null;
PrintWriter out = null;
BufferedReader in = null;
if (args.length != 1){
System.out.println("O Programa deve ser chamado pelo nome + nome do servidor");
System.out.println("Ex: java TCPClient localhost");
System.exit(1);
}
System.out.println("Conectando ao servidor...");
try {
echoSocket = new Socket( args[0] , CommonKeys.PORTA_SERVIDOR);
out = new PrintWriter(echoSocket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(echoSocket
.getInputStream()));
} catch (UnknownHostException e) {
System.err.println("Host não encontrado (" + args[0] + ")");
System.exit(1);
} catch (IOException e) {
System.err.println("Erro ao inicializar I/O para conexao");
System.exit(1);
}
System.out.println("Conectado, digite 'sair' sem as aspas para finalizar");
BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
String userInput;
while ((userInput = stdIn.readLine()) != null) {
out.println(userInput);
String inputLine = in.readLine();
if (inputLine == null){
System.out.println("Servidor terminou a conexão.");
System.out.println("Saindo...");
break;
}
System.out.println("Servidor: " + inputLine.replace("\\n", "\n"));
}
out.close();
in.close();
stdIn.close();
echoSocket.close();
}
}
服务器：
package br.com.redes.server;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import br.com.redes.configuration.CommonKeys;
public class TCPServer {
public static void exibirCabecalho(){
System.out.println("-------------------------");
System.out.println("TCP SERVER");
System.out.println("-------------------------");
}
public static void main(String[] args) throws IOException {
TCPServer.exibirCabecalho();
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket( CommonKeys.PORTA_SERVIDOR );
} catch (IOException e) {
System.err.println("Erro ao iniciar servidor na porta: " + CommonKeys.PORTA_SERVIDOR );
System.exit(1);
}
System.out.println("Iniciando servidor na porta: " + CommonKeys.PORTA_SERVIDOR);
System.out.println("Aguardando cliente...");
Socket clientSocket = null;
try {
clientSocket = serverSocket.accept();
} catch (IOException e) {
System.err.println("Erro ao receber conexoes.");
System.exit(1);
}
PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
String inputLine, outputLine;
System.out.println("Cliente conectado, aguardando caminhos pra leitura...");
while ((inputLine = in.readLine()) != null) {
if (inputLine.equalsIgnoreCase("sair")) {
System.out.println("Sair detectado, fechando servidor...");
break;
}
outputLine = processar(inputLine);
out.println(outputLine);
}
out.close();
in.close();
clientSocket.close();
serverSocket.close();
}
private static String processar(String inputLine) {
final String ARQUIVO_NAO_ENCONTRADO = "arquivo não encontrado.";
final String ARQUIVO_IO = "erro ao ler arquivo.";
System.out.println("Procurando arquivo: " + inputLine);
File f = new File(inputLine);
try {
BufferedReader input = new BufferedReader(new FileReader(f));
String linha = null;
StringBuffer retorno = new StringBuffer();
retorno.append("\\n");
retorno.append("Arquivo encontrado, lendo conteudo: " + inputLine + "\\n");
while (( linha = input.readLine()) != null){
retorno.append(linha + "\\n");
}
retorno.append("fim da leitura do arquivo\\n");
return retorno.toString();
} catch (FileNotFoundException e) {
return ARQUIVO_NAO_ENCONTRADO;
} catch (IOException e) {
return ARQUIVO_IO;
}
}
}