socketJava UDP连接
我正在使用Netbeans IDE尝试在客户端和服务器之间建立UDP连接,这是一个简单的程序,UDPClient将字符串发送到UDPServer,服务器将字符串大写并发送回客户端。我在一个单独的项目中创建了客户端和服务器端
客户端的my类代码UDPClient
:
package udpclient;
import java.io.*;
import java.net.*;
public class UDPClient {
public static void main(String[] args) throws IOException{
//get input from user
BufferedReader user_in = new BufferedReader(
new InputStreamReader(System.in));
//create udp socket connection
DatagramSocket socket = new DatagramSocket();
//creat buffers to process data
byte[] inData = new byte[1024];
byte[] outData = new byte[1024];
//get ip destination wanted
InetAddress IP = InetAddress.getByName("localhost");
//read data from user
System.out.println("Enter Data to send to server: ");
outData = user_in.readLine().getBytes();
/*
* make pkts for interaction
*/
//send pkts
DatagramPacket sendPkt = new DatagramPacket(outData, outData.length, IP, 9876);
socket.send(sendPkt);
//receive pkts
DatagramPacket recievePkt = new DatagramPacket(inData, inData.length);
socket.receive(recievePkt);
System.out.println("Replay from Server: "+recievePkt.getData());
}
}
和我的服务器端类UDPServer
:
package udpserver;
import java.io.*;
import java.net.*;
public class UDPServer {
public static void main(String[] args) throws IOException{
// TODO code application logic
//connection
DatagramSocket socket = new DatagramSocket();
//pkt buffers
byte[] inServer = new byte[1024];
byte[] outServer = new byte[1024];
//receive pkt
DatagramPacket rcvPkt = new DatagramPacket(inServer,inServer.length);
socket.receive(rcvPkt);
//display receive
System.out.println("Packet Received!");
//retrive pkt info to send response to same sender
InetAddress IP = rcvPkt.getAddress();
int port = rcvPkt.getPort();
//process data
String temp = new String(rcvPkt.getData());
temp = temp.toUpperCase();
outServer = temp.getBytes();
//send response packet to sender
DatagramPacket sndPkt = new DatagramPacket(outServer, outServer.length, IP, port);
socket.send(sndPkt);
}
}
确保程序正常运行且无错误输出。服务器根本没有收到数据包,它没有与客户端交互。为什么会这样
# 1 楼答案
问题是服务器代码没有指定端口-它将侦听一个随机可用的端口,而客户端正在发送到9876。要更正此问题,请使用:
(如果您在linux系统上)我强烈建议使用netstat调试此类代码:
将告诉您进程是否正在侦听端口9876。 另一个有用的工具是netcat,可用于发送和接收TCP和UDP:
允许您通过UDP向服务器发送消息
在客户端代码中,还需要将接收到的字节转换回字符串,以获得有意义的输出
# 2 楼答案
您尚未在服务器中指定任何侦听端口,因此服务器在随机可用端口上侦听
在服务器端试试这个