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[英]Communication between server (ANSI C) and client (JAVA) using sockets
[英]Communication between Client and Server using Sockets
好的,这是今天早些时候修订的问题,我提供了有助于解释该问题的代码。 我正在从客户端向服务器发送两条消息。 然后,服务器接收消息并进行处理。 服务器最终尝试将消息发送回客户端(请注意服务器代码“ testmessage”),这是我遇到的问题。 我不是在客户端接收消息,还是从服务器端错误地发送消息。
public class ClientConnection {
String address, language, message;
int portNumber;
Socket clientSocket = null;
public ClientConnection(String lan, String mes, String add, int pn) throws IOException{
address = add;
portNumber = pn;
language = lan;
message = mes;
}
public String createAndSend() throws IOException{
// Create and connect the socket
Socket clientSocket = null;
clientSocket = new Socket(address, portNumber);
PrintWriter pw = new PrintWriter(clientSocket.getOutputStream(),true);
BufferedReader br = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
// Send first message - Message is being correctly received
pw.write(language+"\n");
pw.flush();
// Send off the data
// Send the second message - Message is being correctly received
pw.write(message);
pw.flush();
pw.close();
// Send off the data
// NOTE: Either I am not receiving the message correctly or I am not sending it from the server properly.
String translatedMessage = br.readLine();
br.close();
//Log.d("application_name",translatedMessage); Trying to check the contents begin returned from the server.
return translatedMessage;
}
服务器代码:
public class ServerConnection {
public static void main(String[] args) throws Exception {
// Delete - Using while loop to keep connection open permanently.
boolean status = false;
while( !status){
ServerSocket serverSocket = null;
try {
serverSocket = new ServerSocket(4444);
} catch (IOException e) {
System.err.println("Could not listen on port: 4444.");
System.exit(1);
}
Socket clientSocket = null;
try {
clientSocket = serverSocket.accept();
} catch (IOException e) {
System.err.println("Accept failed.");
System.exit(1);
}
// Delete - Working as of here, connection is established and program runs awaiting connection on 4444
BufferedReader br = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
String language = br.readLine();
String message = br.readLine();
// Test - Works
System.out.println(language);
// Test - Works
System.out.println(message);
// Delete - Working as of here, both messages are passed and applied. Messages are received as sent from client.
TranslateMessage tm = new TranslateMessage();
String translatedMessage = tm.translateMessage(language, message);
// NOTE: This seems to be where I am going wrong, either I am not sending the message correctly or I am not receiving it correctly..
// PrintWriter writer = new PrintWriter(new BufferedOutputStream(clientSocket.getOutputStream()));
PrintWriter pw = new PrintWriter(clientSocket.getOutputStream(),true);
// Send translation back
System.out.println(translatedMessage);
// pw.write(translatedMessage+"\n");
pw.write("Return test"); // Test message!
pw.flush();
// Send off the data
pw.close();
br.close();
clientSocket.close();
serverSocket.close();
}
}
}
代码有点混乱,我可以看到一些重复的地方,我在出现问题的地方发表了评论。
谢谢你的帮助!
您正在使用BufferedReader.readLine()从服务器读取响应,但是在测试用例中,您发送的字符串未以\\ n或\\ r \\ n终止,因此它将无法获得该行。我可以从文档中看出...
public String readLine()
throws IOException
Read a line of text. A line is considered to be terminated by any one of a line feed ('\n'), a carriage return ('\r'), or a carriage return followed immediately by a linefeed.
Returns:
A String containing the contents of the line, not including any line-termination characters, or null if the end of the stream has been reached
另一个建议...
在编写这样的请求响应协议时,我不会依靠行尾来终止请求或响应。 通常,我会使用完全格式化的JSON字符串,或者我的首选是二进制协议,其中所有请求和响应都以二进制计数为前缀(通常为4字节,bigendian /网络字节顺序)。 然后,客户端和服务器读取这4个字节,然后读取随后的字节数。 这可以处理通常在网络连接上发生的数据包碎片,还有助于避免恶意用户发送永不终止的长字符串而引起的DOS攻击。
在Java中,可以使用ByteBuffer.order()处理双端数字。
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