同一台计算机上的UDP连接。 1服务器。多个客户

Question

工作Qt框架..，需要得到给出requiremets

的解决方案我已经在一台服务器和2个客户端我的电脑： IP1，IP2，IP3是端口。

我的服务器上IP1听，端口号9999 我要发送数据（数据包）到服务器，然后服务器需要我的客户进行回应。 所以我可以知道客户端IP地址和客户端端口号。

客户端IP地址和端口如何知道服务器？，这是获取响应回到客户端所必需的。

注意：我在同一台PC上运行server，client1和client2。

Answer 1

不确定Qt框架，但使用正常的套接字命令bind到特定的IP和端口。

handle = socket(AF_INET, SOCK_DGRAM, 0); 

// my local computer 
struct sockaddr_in addr_loc; 
memset(&addr_loc, 0, sizeof(addr_loc)); 
addr_loc.sin_family = AF_INET; 
addr_loc.sin_port = htons(localPort); 
addr_loc.sin_addr.s_addr = htonl(localAddr); 
bind(handle, (struct sockaddr*)&addr_loc, sizeof(addr_loc)); 

// the remote location 
struct sockaddr_in addr_rem; 
memset(&addr_rem, 0, sizeof(addr_rem)); 
addr_rem.sin_family = AF_INET; 
addr_rem.sin_port = htons(remotePort); 
addr_rem.sin_addr.s_addr = htonl(remoteAddr); 
sendto(handle, packetData, packetLength, 0, (struct sockaddr *)&addr_rem, sizeof(addr_rem)); 

Answer 2

，你将有服务器监听本地主机，127.0.0.1，然后每个客户端将连接到本地主机（127.0.0.1），该服务器监听端口上。在这里，我将展示它的外观。

服务器的代码可能是这样的：

#include <unistd.h> 
#include <sys/types.h> 
#include <sys/socket.h> 
#include <netinet/in.h> 
#include <arpa/inet.h> 
#include <stdio.h> 
#include <stdlib.h> 
#include <string.h> 
#include <netdb.h> 

int main() { 
    struct addrinfo hints, *res; 
    int sockfd; 
    int byte_count; 
    socklen_t fromlen; 
    struct sockaddr_storage addr; 
    char buf[512]; 
    char ipstr[INET6_ADDRSTRLEN]; 

    // get host info, make socket, bind it to port 9999 
    memset(&hints, 0, sizeof hints); 
    hints.ai_family = AF_UNSPEC; // use IPv4 or IPv6, whichever 
    hints.ai_socktype = SOCK_DGRAM; 
    hints.ai_flags = AI_PASSIVE; 
    getaddrinfo(NULL, "9999", &hints, &res); 
    sockfd = socket(res->ai_family, res->ai_socktype, res->ai_protocol); 
    bind(sockfd, res->ai_addr, res->ai_addrlen); 

    // no need to accept(), just recvfrom(): 
    fromlen = sizeof addr; 
    byte_count = recvfrom(sockfd, buf, sizeof buf, 0, (sockaddr*)&addr, &fromlen); 

    printf("recv()'d %d bytes of data in buf\n", byte_count); 
    printf("from IP address %s\n", 
      inet_ntop(addr.ss_family, 
      (const void*)(&((struct sockaddr_in *) &addr)->sin_addr), ipstr, sizeof ipstr)); 

    return 0; 
} 

你可以尝试在该服务器通过NC与-vu选项监听终端：

[email protected]:~# nc -vu localhost 9999 

，应该从这样的服务器获得的输出：

recv()'d 29 bytes of data in buf 
from IP address 127.0.0.1 

客户端代码：

#define DEST_PORT 9999 
#define DEST_IP "127.0.0.1" 

int main(int argc, char** argv) { 
    char *secret_message = "The Cheese is in The Toaster"; 

    int dgram_socket; 
    struct sockaddr_in dest_addr; 

    // now with UDP datagram sockets: 
    // datagram sockets and recvfrom() 
    dest_addr.sin_family = AF_INET; 
    /* short, network byte order */ 
    dest_addr.sin_port = htons(DEST_PORT); 
    dest_addr.sin_addr.s_addr = inet_addr(DEST_IP); 

    /* zero the rest of the struct */ 
    memset(&(dest_addr.sin_zero), 0, 8); 

    dgram_socket = socket(dest_addr.sin_family, SOCK_DGRAM, 0); 


    // send secret message normally: 
    sendto(dgram_socket, secret_message, strlen(secret_message) + 1, 0, 
      (struct sockaddr*) &dest_addr, sizeof dest_addr); 

    return 0; 
} 

再次，发射时你应该从服务器的输出与此类似：

recv()'d 29 bytes of data in buf 
from IP address 127.0.0.1 

Answer 3

How client IP address and port knows to the server ?, 
    Ans: When datagram is recieved(readyRead signal is emited), you can use readDatagram API 
    socketServer.readDatagram(buffer.data(),buffer.size(),&sender,&port); 
    sender = IPaddress of client 
    por = portNumber of client. 

这里是同一本地主机上使用Qt的QUdpSocket提供，1 UDP Sever的解决方案，用多个客户端，测试它正在工作。注释的代码，在必要

有两个控制台应用程序（UDPServer和UDPClient）

How to test 
    1. Run UDPServer, it will listen on port 9999 
    2. Run UDPClient(First instance) 
    3. Run UDPClient(second instance) 

Result: 
    Please check below screenshot 

UDPServer代码

>的main.cpp

int main(int argc, char *argv[]) 
{ 
    QCoreApplication a(argc, argv); 
    UDPServer server; 
    return a.exec(); 
} 

> UDPServer。ħ

#ifndef UDPSERVER_H 
    #define UDPSERVER_H 
    #include <QObject> 
    #include <QUdpSocket> 

    class UDPServer : public QObject 
    { 
     Q_OBJECT 
    public: 
     explicit UDPServer(QObject *parent = 0); 
     void WriteData(const QString&); 

    public slots: 
     void readReady(); 
    private: 
     QUdpSocket socketServer; 

    }; 
    #endif // UDPSERVER_H 

> UDPServer.cpp

#include "UDPServer.h" 
UDPServer::UDPServer(QObject *parent) :QObject(parent),socketServer(this) 
{ 
    qDebug()<<"I am UDP server, listening on 9999"; 
    // Listen to 9999 port server 
    socketServer.bind(QHostAddress::LocalHost,9999); 
    connect(&socketServer,SIGNAL(readyRead()),this,SLOT(readReady())); 

} 

void UDPServer::readReady() 
{ 
    QByteArray buffer; 
    buffer.resize(socketServer.pendingDatagramSize()); 
    QHostAddress sender; 
    quint16 port; 
    socketServer.readDatagram(buffer.data(),buffer.size(),&sender,&port); 
    qDebug()<<"Datagram Recieved From"; 
    qDebug()<<"Client IP" << sender.toString(); 
    qDebug()<<"Client Port Number " << port; 
    qDebug()<<"\n\n"; 

    // Write to the client,need to specify the client port number. 
    QByteArray clientData; 
    clientData.append("data"); 
    socketServer.writeDatagram(clientData, QHostAddress::LocalHost, port); 
} 

UDPClient代码

>的main.cpp

#include <QtCore/QCoreApplication> 
#include "udpclient.h" 

int main(int argc, char *argv[]) 
{ 
    QCoreApplication a(argc, argv); 
    UDPClient client; 
    client.WriteData("What is my IP");  
    return a.exec(); 
} 

> udpclient.h

#ifndef UDPCLIENT_H 
#define UDPCLIENT_H 

#include <QObject> 
#include <QUdpSocket> 

class UDPClient : public QObject 
{ 
    Q_OBJECT 
public: 
    explicit UDPClient(QObject *parent = 0); 
    void WriteData(const QString&); 
public slots: 
    void readReady(); 

private: 
    QUdpSocket clientSocket; 

}; 

#endif // UDPCLIENT_H 

> udpclient.cpp

#include "udpclient.h" 


UDPClient::UDPClient(QObject *parent) :QObject(parent), clientSocket(this) 
{  
    qDebug()<<"I am your client"; 
    connect(&clientSocket,SIGNAL(readyRead()),this,SLOT(readReady())); 
} 

void UDPClient::WriteData(const QString& data) 
{ 
    QByteArray clientData; 
    clientData.append(data);  
    // write to the port, listening by the server. 
    qDebug()<<"Writing datagram to 9999 port"; 
    clientSocket.writeDatagram(clientData, QHostAddress::LocalHost, 9999); 

} 

void UDPClient::readReady() 
{ 
    // got response from server, so clientSoclet port number can get. 
    qDebug()<< "Reacieved response from server through my port(Client port No):" << clientSocket.localPort(); 

    QByteArray buffer;  
    buffer.resize(clientSocket.pendingDatagramSize());   

    QHostAddress sender;  
    quint16 port; 
    clientSocket.readDatagram(buffer.data(),buffer.size(),&sender,&port);  
    // To read server IP 
    qDebug()<< "Server IP Responded" << sender.toString(); 
    qDebug()<< "Server Port Number" << port;  
}