使用recvfrom在UDP上关闭客户端

Question

大家好，我对网络世界还很陌生，我已经编写了udp客户端-服务器程序。我发现困难的是如何在服务器完成数据发送后关闭客户端程序（.exe）。我当时在考虑使用recvfrom（）的返回值，但这最终使程序无法控制最后打印的else节（ 10054 失败）。这是我的客户端代码：-

#define _WIN32_WINNT 0x0501

#include<winsock2.h>
#include<stdio.h>
#include <dirent.h>
#include<string.h>
#define DEFAULT_PORT 27015
#define DEFAULT_BUFLEN 1400
#define DEFAULT_FLEN 25
#define DEFAULT_SERVER_ADDR "127.0.0.1"



int main(){
    int iResult, bufflen = DEFAULT_BUFLEN,fLen = DEFAULT_FLEN;
    SOCKET client_socket = INVALID_SOCKET;
    WSADATA wsaData;
    struct sockaddr_in server;
    int sLen = sizeof(server);
    char recvBuf[DEFAULT_BUFLEN] ="",filename[DEFAULT_FLEN] ;

    iResult = WSAStartup(MAKEWORD(2,2), &wsaData);

if(iResult != 0){
    printf("WSAStartup failed : %d\n",WSAGetLastError());
        return -1;
}

//creating unbound socket
client_socket = socket(AF_INET, SOCK_DGRAM, 0);
if(client_socket == INVALID_SOCKET){
    printf("Error at socket(): %d\n", WSAGetLastError());
    WSACleanup();
    return -1;
}

memset((char *) &server, 0, sizeof(server));
server.sin_family = AF_INET;
server.sin_addr.s_addr = inet_addr(DEFAULT_SERVER_ADDR);
server.sin_port = DEFAULT_PORT;

printf("Enter filename :: ");
scanf("%[^\n]s",filename);
iResult = sendto(client_socket,filename,fLen,0,(struct sockaddr *)&server, sLen);

if(iResult == SOCKET_ERROR){
    printf("sendto() failed with error code : %d" , WSAGetLastError());
    return -1;
}   

    int sendno = 1,bytes_written = 0, ACK ;
    memset(recvBuf,'\0',sizeof(recvBuf));
    FILE *fp = NULL;
    fp  = fopen(filename,"ab");
    while(iResult != -1){
    iResult = recvfrom(client_socket, recvBuf, bufflen, 0, (struct sockaddr *) &server, &sLen);
    if (iResult > 0){
        ACK = sendto(client_socket,recvBuf,bufflen,0,(struct sockaddr *)&server, sLen);
        printf("ACK Sent = %d\n",ACK);
         printf("Byte(s) received :: %d iteration %d\n",iResult,sendno);
        sendno++;
        bytes_written = fwrite(recvBuf,sizeof(char),iResult,fp);
        printf("bytes written %d\n",bytes_written);
        memset(recvBuf,'\0',sizeof(recvBuf));
    }
    else if (iResult == 0){
    printf("Connection closed\n");
    break;
    }
    else{
        printf("Recevied failed %d\n",WSAGetLastError());
    }
    }

//cleanup
closesocket(client_socket);
WSACleanup();

return 0;
}