我的程序不发送消息或没有接收到套接字，ip是127.0.0.1

当我使用套接字时，程序服务器进程不会收到来自客户端进程/类的任何消息。用户的输入端口是5555，但当程序退出客户端的构造函数时，sin的端口号不匹配（我认为是因为htons），ip地址也是如此。请帮我修一下。

这是我的服务器代码：

#include "SocketUDP.h"
/*
* class constructor
*/
SocketUDP::SocketUDP() {
    sock = socket(AF_INET, SOCK_DGRAM, 0);
    if (sock < 0)
        perror("error creating socket");
}
/*
* class destructor
*/
SocketUDP::~SocketUDP() {
    close(sock);
}
/*
* this function recieves a message from client/server
* @param - the length of the message
*/
std::string SocketUDP::RecieveMessage(){
    unsigned int from_len = sizeof(struct sockaddr_in);
    char buffer[4096];
    memset(&buffer, 0, sizeof(buffer));
    int bytes = recvfrom(sock, buffer, sizeof(buffer), 0,
        (struct sockaddr *) &from, &from_len);
    if (bytes < 0)
        perror("error reading from socket");
    return std::string(buffer);
}

这是客户：

  #include "UDPClient.h" 
  /*
  * class constructor
  */
  UDPClient::UDPClient(char * ip, int port) {
      memset(&sin, 0, sizeof(sin));
      sin.sin_addr.s_addr = inet_addr(ip);
      sin.sin_family = AF_INET;
      sin.sin_port = htons(port);
  }
 /*
 * class destructor
 */
UDPClient::~UDPClient() {
    // TODO Auto-generated destructor stub
}
 /*
 * this function sends a message to the client/server
 * @param - the message
  */
  int UDPClient::SendMessage(std::string st){
      int sent_bytes = sendto(sock, st.c_str(), st.length(), 0,
            (struct sockaddr *) &sin, sizeof(sin));
      if (sent_bytes < 0)
          perror("error writing to socket");
      return sent_bytes;
  }