자바로 만든 서버와 c 로 만든 클라이언트간에 데이타는 어떻게

서버에 \r\n을 어디에 추가해야되나요??
클라이언트에 fflush를 쓰려는데 어디에써야하나요??

#include
#include
#include
#include
#include
#include
#define SERVER_PORT 3000

int Socket(int family, int type, int protocol);
void Bind(int sockfd, const struct sockaddr * socketaddr, socklen_t addrlen);
void Listen(int sockfd, int backlog);
int Accept(int sockfd, struct sockaddr* cliaddr, socklen_t *addrlen);

int main(void)
{
int server_socket;
int client_socket;

int nSockOpt;

struct sockaddr_in server_addr;
struct sockaddr_in client_addr;
int addrsize, msgsize;

char BUFF[1024] = { 0, };
fd_set readfd;
int maxfd;
int client_index;
int start_index;
int client_fd[5] = { 0 };
server_socket = Socket(AF_INET, SOCK_STREAM, 0);
server_addr.sin_family = AF_INET;
server_addr.sin_port = htons(SERVER_PORT);
server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
memset(&(server_addr.sin_zero), 0, 8);
nSockOpt = 1;
setsockopt(server_socket, SOL_SOCKET, SO_REUSEADDR, &nSockOpt, sizeof(nSockOpt));
Bind(server_socket, (struct sockaddr*)&server_addr, sizeof(struct sockaddr));

Listen(server_socket, 10);
FD_ZERO(&readfd);
maxfd = server_socket;
client_index = 0;

while (1)
{
FD_SET(server_socket, &readfd);

for (start_index = 0; start_index < client_index; start_index++)
{
FD_SET(client_fd[start_index], &readfd);

if (client_fd[start_index] > maxfd)
maxfd = client_fd[start_index];
}
maxfd = maxfd + 1;

select(maxfd, &readfd, NULL, NULL, NULL);

if (FD_ISSET(server_socket, &readfd))
{
if (client_index == 5)
break;
addrsize = sizeof(struct sockaddr_in);
client_socket = Accept(server_socket, (struct sockaddr*)&server_addr, &addrsize);
FD_SET(client_socket, &readfd);

client_fd[client_index] = client_socket;
client_index++;

}

for (start_index = 0; start_index < client_index; start_index++)
{
if (FD_ISSET(client_fd[start_index], &readfd))
{
memset(BUFF, '\0', sizeof(BUFF));

msgsize = read(client_fd[start_index], BUFF, sizeof(BUFF));
if (msgsize <= 0)
continue;
printf("Client Message>>%s", BUFF);

strcpy(BUFF, "Hello World!");

msgsize = strlen(BUFF);
write(client_fd[start_index], BUFF, msgsize);
}
}
}
return 0;

}
int Socket(int family, int type, int protocol)
{
int result = 0;
result = socket(family, type, protocol);
if (result == -1)
{
printf("Socket Contructing Error\n");
exit(0);
}
return result;
}
void Bind(int sockfd, const struct sockaddr * socketaddr, socklen_t addrlen)
{
int result = 0;
result = bind(sockfd, socketaddr, addrlen);
if (result == -1)
{
printf("Socket Binding Error\n");
exit(0);
}
else
{
printf("Success Binding\n");
}

}
void Listen(int sockfd, int backlog)
{
int result = 0;
result = listen(sockfd, backlog);
if (result == -1)
{
printf("Listening Error\n");
exit(0);
}
else
{
printf("Success Listening\n");
}
}

int Accept(int sockfd, struct sockaddr* cliaddr, socklen_t *addrlen)
{
int result = 0;
result = accept(sockfd, cliaddr, addrlen);
if (result == -1)
{
printf("Accept Error\n");
exit(0);
}
else
{
printf("Success Accept\n");
}
return result;

}

================================================
package com.example.rasp;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class SensormainActivity extends Activity {

private Socket socket;
BufferedReader socket_in;
PrintWriter socket_out;
EditText input;
Button button;
TextView output;
String data;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.sensor);

input = (EditText) findViewById(R.id.input);
button = (Button) findViewById(R.id.button);
output = (TextView) findViewById(R.id.output);
button.setOnClickListener(new OnClickListener(){
public void onClick(View v){
String data = input.getText().toString();
Log.w("NETWORK",""+data);
if(data != null){
socket_out.println(data);
}
}
});
Thread worker = new Thread() {
public void run() {
try {
socket = new Socket("203.250.133.240", 3000);
socket_out = new PrintWriter(socket
.getOutputStream(), true);
socket_in = new BufferedReader(
new InputStreamReader(socket
.getInputStream()));
} catch (IOException e) {
e.printStackTrace();
}
try {
while (true) {
data = socket_in.readLine();
output.post(new Runnable() {
public void run() {
output.setText(data);
}
});
}
} catch (Exception e) {
}
}
};

worker.start();
}

@Override
protected void onStop() {
super.onStop();
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}