[英]UDP respond on connected socket
因此,我已经使用TCP编程了一段时间,并决定选择UDP。 我不太确定需要做些什么才能使我在WAN上双向通信(或者通过lan进行通信,因为可以打开两个端口,所以在lan上更容易),一旦我从客户端发送信息到服务器如何在该套接字上响应。 有没有直接连接的方法?
(当前快速功能)
int udpsock(int port, const char* addr){
int handle = socket( AF_INET, SOCK_DGRAM, IPPROTO_UDP );
if (handle < 1)
return -1;
sockaddr_in address;
address.sin_family = AF_INET;
if (addr == INADDR_ANY)
address.sin_addr.s_addr = INADDR_ANY;
else
address.sin_addr.s_addr = inet_addr(addr);
address.sin_port = htons( (unsigned short) port );
if ( bind( handle, (const sockaddr*) &address, sizeof(sockaddr_in) ) < 0 )
return -1;
return handle;
}
string recvudp(int sock,const int size){
sockaddr_in SenderAddr;
int SenderAddrSize = sizeof (SenderAddr);
char buf[size];
int retsize = recvfrom(sock, buf, sizeof(buf), 0, (SOCKADDR *) & SenderAddr, &Sen derAddrSize);
if (retsize == -1){
cout << "\nRecv Error : " << WSAGetLastError();
if (WSAGetLastError() == WSAEWOULDBLOCK || WSAGetLastError() == 0){
return "";
}
return "\0";
}
else if (retsize < size){
buf[retsize] = NULL;
}
return buf;
}
int sendudp(string str, string ip, unsigned short port, int sock){
sockaddr_in dest;
dest.sin_family = AF_INET;
dest.sin_addr.s_addr = inet_addr( ip.c_str() );
dest.sin_port = htons( port );
int ret = sendto(sock,str.c_str(),str.size(),0, (sockaddr*)&dest,sizeof(dest));
if (ret == -1){
cout << "\nSend Error Code : " << WSAGetLastError();
}
return ret;
}
有了这个,很容易制作一个带有端口xxxx的套接字,并让合作伙伴在该端口上发送数据以将数据发送给客户端,第四部分是我遇到麻烦的地方=]
使您的sendudp
函数采用sockaddr_in
。 您可以从recvfrom
获得recvfrom
,并将其传递给sendto
。 或者,传递接收到的sockaddr_in
进行connect
,然后使用send
。
我假设您发布的功能应在客户端和服务器之间共享。 为了实现这一点,需要对其进行略微修改。 例如,在服务器端, recvudp
应该返回客户端地址(可能作为out参数),以后再用于将消息发送回该地址。 此外,由于客户端地址结构已经填充(在服务器端的recvudp
或在客户端手动地),我们可以将其传递给sendudp
作为其参数。
我已经玩了一点,并在Visual Studio 2010中创建了两个简单的项目:UDP服务器和客户端。 它们都使用上述共享功能。 该代码远非完美,仅旨在显示基本的UDP套接字通信。
Shared.h:
#ifndef SHARED_H
#define SHARED_H
#include <winsock2.h>
#include <string>
int udpsock(int port, const char* addr);
std::string recvudp(int sock, const int size, sockaddr_in& SenderAddr, int& SenderAddrSize);
int sendudp(std::string str, sockaddr_in dest, int sock);
#endif
Shared.cpp:
#include "Include\shared.h" // path to header - you might use different one
#include <iostream>
using namespace std;
int udpsock(int port, const char* addr)
{
int handle = socket( AF_INET, SOCK_DGRAM, IPPROTO_UDP );
if (handle < 1)
return -1;
sockaddr_in address;
address.sin_family = AF_INET;
if (addr == INADDR_ANY)
address.sin_addr.s_addr = INADDR_ANY;
else
address.sin_addr.s_addr = inet_addr(addr);
address.sin_port = htons( (unsigned short) port );
if ( bind( handle, (const sockaddr*) &address, sizeof(sockaddr_in) ) < 0 )
return -1;
return handle;
}
// function should return sender address info (for the code the server)
string recvudp(int sock, const int size, sockaddr_in& SenderAddr, int& SenderAddrSize)
{
// TODO: use std::vector<char> here instead of char array
char* buf = 0;
buf = new char[size];
int retsize = recvfrom(sock, buf, size, 0, (sockaddr*) &SenderAddr, &SenderAddrSize);
if(retsize == -1)
{
cout << "\nRecv Error : " << WSAGetLastError();
if (WSAGetLastError() == WSAEWOULDBLOCK || WSAGetLastError() == 0)
{
return "";
}
return "\0";
}
else if (retsize < size)
{
buf[retsize] = NULL;
}
string str(buf);
delete[] buf;
return str;
}
// On the client side, prepare dest like this:
// sockaddr_in dest;
// dest.sin_family = AF_INET;
// dest.sin_addr.s_addr = inet_addr(ip.c_str());
// dest.sin_port = htons(port);
int sendudp(string str, sockaddr_in dest, int sock)
{
int ret = sendto(sock,str.c_str(),str.size(),0, (sockaddr*)&dest,sizeof(dest));
if (ret == -1)
{
cout << "\nSend Error Code : " << WSAGetLastError();
}
return ret;
}
服务器:main.cpp:
#include <winsock2.h>
#include <string.h>
#include <iostream>
#include "..\Shared\Include\shared.h"
// Link with ws2_32.lib
#pragma comment(lib, "Ws2_32.lib")
#define SERVER_PORT 27015
#define MAX_MSG 1024
using namespace std;
int main(int argc, char *argv[])
{
WSADATA wsaData;
int nResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
if(nResult != NO_ERROR)
{
cout << "WSAStartup failed with error: " << nResult << endl;
return 1;
}
sock = udpsock(SERVER_PORT, "127.0.0.1");
cout << "Waiting for datagram on port: " << SERVER_PORT << endl;
while(1)
{
sockaddr_in clientAddr;
// receive message
int clientAddrLen = sizeof(clientAddr);
cout << "Received message from the client: " << recvudp(sock, MAX_MSG, clientAddr, clientAddrLen) << endl;
sendudp("Hello from server!", clientAddr, sock);
}
WSACleanup();
return 0;
}
客户端:main.cpp:
#include <winsock2.h>
#include <iostream>
#include "..\Shared\Include\shared.h"
using namespace std;
#define MAX_MSG 1024
// Link with ws2_32.lib
#pragma comment(lib, "Ws2_32.lib")
int main(int argc, char* argv[])
{
WSADATA wsaData;
int nResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
if (nResult != NO_ERROR)
{
cout << "WSAStartup failed with error: " << nResult << endl;
return 1;
}
SOCKET sock = INVALID_SOCKET;
// Create a socket for sending data - it does not need to be binded like listening socket!
sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if(sock == INVALID_SOCKET)
{
cout << socket failed with error: " << WSAGetLastError() << endl;
WSACleanup();
return 1;
}
unsigned short Port = 27015;
sockaddr_in dest;
dest.sin_family = AF_INET;
dest.sin_addr.s_addr = inet_addr("127.0.0.1");
dest.sin_port = htons(Port);
sendudp("Hello from client!", dest, sock);
sockaddr_in RecvAddr;
int recvaddrlen = sizeof(RecvAddr);
cout << "Received message from the server: " << recvudp(sock, MAX_MSG, RecvAddr, recvaddrlen) << endl;
cout << "Closing socket..." << endl;
nResult = closesocket(sock);
if(nResult == SOCKET_ERROR)
{
cout << "closesocket failed with error: " << WSAGetLastError() << endl;
WSACleanup();
return 1;
}
WSACleanup();
return 0;
}
如果您运行两次客户端,则输出为:
服务器:
等待端口上的数据报:27015
收到客户端的消息:客户端您好!
收到客户端的消息:客户端您好!
客户:
从服务器收到的消息:您好,服务器!
合闸插座...
UDP是无连接协议,服务器只需要在UDP端口上开始侦听,客户端就可以立即发送数据(数据报),而无需建立连接(例如,在TCP中使用connect()
/ accept()
)。
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