简介

UDP协议与TCP协议一样用于处理数据包，在OSI模型中，两者都位于传输层，处于IP协议的上一层。UDP有不提供数据包分组、组装和不能对数据包进行排序的缺点，也就是说，当报文发送之后，是无法得知其是否安全完整到达的。

代码实现

#ifndef _SOCKET_HPP_

#define _SOCKET_HPP_

#include 

#include 

#include 

#include 

#include 

#include 

#define MAX_BUFFER 1024

using namespace std;

namespace Socket

{ 



typedef int Socket;

typedef string Ip;

typedef unsigned int Port;

typedef string Data;

typedef struct

{ 



Ip ip;

Port port;

}Address;

typedef struct

{ 



Address address;

Data data;

}Datagram;

struct sockaddr_in* to_sockaddr(Address* a)

{ 

   struct sockaddr_in* ret;

ret=(struct sockaddr_in*) malloc (sizeof(struct sockaddr_in));

ret->sin_family = AF_INET;

inet_aton(a->ip.c_str(),&(ret->sin_addr));

ret->sin_port=htons(a->port);

return ret;

}

Address* from_sockaddr(struct sockaddr_in* address)

{ 

   Address* ret;

ret=(Address*)malloc(sizeof(Address));

ret->ip = inet_ntoa(address->sin_addr);

ret->port = ntohs(address->sin_port);

return ret;

}

class Exception

{ 



private:

string _message;

public:

Exception(string error) { 

 this->_message = error; }

virtual const char* what() { 

 return this->_message.c_str(); }

};

class UDP

{ 



private:

Socket _socket_id;

bool _binded;

public:

UDP(void);

~UDP(void);

void close(void);

void bind(Port port);

void send(Ip ip, Port port, Data data);

Datagram receive();

};

UDP::UDP(void)

{ 



this->_socket_id = socket(AF_INET, SOCK_DGRAM, 0);   

if (this->_socket_id == -1) throw Exception("[Constructor] Cannot create socket");           

this->_binded = false;

}

UDP::~UDP(void)

{ 



}

void UDP::close(void)

{ 



shutdown(this->_socket_id, SHUT_RDWR);

}

void UDP::bind(Port port)

{ 



struct sockaddr_in address;

address.sin_family = AF_INET;

address.sin_addr.s_addr=htonl(INADDR_ANY);

address.sin_port=htons(port);

if (this->_binded)

{ 



this->close();

this->_socket_id = socket(AF_INET, SOCK_DGRAM, 0);

}

// ::bind() calls the function bind() from  (outside the namespace) 

if (::bind(this->_socket_id, (struct sockaddr*)&address, sizeof(struct sockaddr_in)) == -1)

{ 



stringstream error;

error << "[listen_on_port] with [port=" << port << "] Cannot bind socket";

throw Exception(error.str());

}

this->_binded = true;

}

void UDP::send(Ip ip, Port port, Data data)

{ 



struct sockaddr_in address;

address.sin_family = AF_INET;

address.sin_port = htons(port);

inet_aton(ip.c_str(), &address.sin_addr);

if (sendto(this->_socket_id, (void*)data.c_str(), data.length() + 1, 0, (struct sockaddr*)&address, sizeof(struct sockaddr_in)) == -1)

{ 



stringstream error;

error << "[send] with [ip=" << ip << "] [port=" << port << "] [data=" << data << "] Cannot send";

throw Exception(error.str());

}

}

Datagram UDP::receive()

{ 



int size = sizeof(struct sockaddr_in);

char *buffer = (char*)malloc(sizeof(char) * MAX_BUFFER);

struct sockaddr_in address;

Datagram ret;

if (recvfrom(this->_socket_id, (void*)buffer, MAX_BUFFER, 0, (struct sockaddr*)&address, (socklen_t*)&size) == -1) throw Exception("[receive] Cannot receive");

ret.data = buffer;

ret.address.ip = inet_ntoa(address.sin_addr);

ret.address.port = ntohs(address.sin_port);

free(buffer);

return ret;

}

}

#endif // _SOCKET_HPP_

使用示例

UDP server

#include 

#include "Socket.hpp"

using namespace std;

int main(void)

{ 



try

{ 



Socket::UDP sock;

sock.bind(2000);

Socket::Datagram received = sock.receive();

cout << received.data << endl;

sock.send("127.0.0.1", 3000, "response");

sock.close();

}

catch (Socket::Exception &e)

{ 



cout << e.what() << endl;

}

return 0;

}

UDP client

#include 

#include "Socket.hpp"

using namespace std;

int main(void)

{ 



try

{ 



Socket::UDP sock;

sock.bind(3000);

sock.send("127.0.0.1", 2000, "request");

Socket::Datagram received = sock.receive();

cout << received.data << endl;

sock.close();

}

catch (Socket::Exception &e)

{ 



cout << e.what() << endl;

}

return 0;

}