package net1;import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.concurrent.TimeUnit;public class Client_ {
public static void main(String[] args){
try {
Socket client=new Socket("locahost",8888);
OutputStream out=client.getOutputStream();

OutputStreamWriter writer=new OutputStreamWriter(out);
writer.write("a message");

writer.flush();

TimeUnit.SECONDS.sleep(40);
} catch (UnknownHostException e) {

e.printStackTrace();
} catch (IOException e) {

e.printStackTrace();
} catch (InterruptedException e) {
// TODO 自动生成 catch 块
e.printStackTrace();
}

}


}
上面是客户端package net1;import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;public class Server_ {
public static void main(String[] args){
try {
ServerSocket server=new ServerSocket(8888);
System.out.println("server start");

Socket client=server.accept();
System.out.println("recive client");

InputStream in=client.getInputStream();
InputStreamReader reader=new InputStreamReader(in);

int i=0;
while(true){
i=reader.read();
if (i==-1){
break;
}
System.out.println((char) i);
}
} catch (IOException e) {
e.printStackTrace();
}
}}
以上是服务器端问题:运行服务器时:只有server start  接着运行客户端:
java.net.UnknownHostException: locahost
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:177)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:364)
at java.net.Socket.connect(Socket.java:507)
at java.net.Socket.connect(Socket.java:457)
at java.net.Socket.<init>(Socket.java:365)
at java.net.Socket.<init>(Socket.java:178)
at net1.Client_.main(Client_.java:13)小弟初学java,不知道问题出在哪里?