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如何打开两个具有相同本地端口的客户端套接字，如java。在 Java 中，我们可以在创建 DatagramPacket 时提及源端口。我正在尝试进行 UDP 打孔。如果我做错了什么，请纠正我。

我在这里添加了我的代码。

void UDPClientConnect ( string IP , string Port ) 
{ 
    WSADATA wsa;


if ( WSAStartup(MAKEWORD(2,2),&wsa) != 0 )
{
    printf ( "startup failed %d\n" , WSAGetLastError() ) ;
    return ;
}
int reuse = 1 ; 
SOCKET s = socket ( AF_INET , SOCK_DGRAM , IPPROTO_UDP ) ;
setsockopt(s, SOL_SOCKET, SO_REUSEADDR,(char*) &reuse, sizeof(int)); 

struct sockaddr_in si_other;
int slen=sizeof(si_other);
char buf[BUFLEN];
char message[BUFLEN];

int p = atoi ( Port.c_str() ) ;

memset((char *) &si_other, 0, sizeof(si_other));
si_other.sin_family = AF_INET;

si_other.sin_port = htons(p);
si_other.sin_addr.S_un.S_addr = inet_addr( IP.c_str() );

strcpy_s ( message , "Hello" ) ;


//send the message
if ( sendto ( s , message , strlen(message) , 0 , (struct sockaddr *) &si_other , slen ) == SOCKET_ERROR)
{
    printf ( "sendto() failed with error code : %d" , WSAGetLastError() ) ;
   return ;
}

//receive a reply and print it
memset ( buf , '\0' , BUFLEN ) ;
//try to receive some data, this is a blocking call
if ( recvfrom ( s , buf , BUFLEN , 0 , (struct sockaddr *) &si_other , &slen ) == SOCKET_ERROR )
{
    printf("recvfrom() failed with error code : %d" , WSAGetLastError());
    return ;
}

struct sockaddr_in localAddress;
int addrlen = sizeof(localAddress) ;

getsockname ( s , (struct sockaddr*)&localAddress , &addrlen ) ;

USHORT LocalPort = localAddress.sin_port ;
IN_ADDR localAddr = localAddress.sin_addr ;

printf("local address: %s\n", inet_ntoa( localAddress.sin_addr));
printf("local port: %d\n", (int) ntohs(localAddress.sin_port));

printf ( "\n******************************************\n\n" ) ;

int pos = 1 ;
CStringA CBuff = CStringA ( buf ) ;

string RemortPort = CBuff.Tokenize ( "-" , pos ) ;
string RemortIp = CBuff.Tokenize ( "-" , pos ) ;


reuse = 1 ;

SOCKET Sock_Reuse = socket ( AF_INET , SOCK_DGRAM , IPPROTO_UDP ) ;

setsockopt( Sock_Reuse , SOL_SOCKET, SO_REUSEADDR,(char*) &reuse, sizeof(int)); // optional, but recommended

struct sockaddr_in sin;
memset(&sin,0,sizeof(sin));
sin.sin_family=AF_INET;
sin.sin_port=htons(LocalPort);
sin.sin_addr.s_addr=INADDR_ANY;

if ( SOCKET_ERROR == connect(Sock_Reuse,(struct sockaddr *)&sin,sizeof(struct sockaddr_in)))
{
    printf ( "bind failed %d" , WSAGetLastError() ) ;
}

closesocket ( Sock_Reuse ) ;
closesocket ( s ) ;
WSACleanup ( ) ;

}

以同样的方法，我试图用相同的端口打开新的套接字。

检查我试图在 C/C++ 中这样做的这个 Java 代码。这不可能 ？？

import java.io.* ;
import java.net.* ;

public class UDPHolePunchingClient {

public static void main(String[] args) throws Exception {
    // prepare Socket
    DatagramSocket clientSocket = new DatagramSocket();

    // prepare Data
    byte[] sendData = "Hello".getBytes();

    // send Data to Server with fix IP (X.X.X.X)
    // Client1 uses port 7070, Client2 uses port 7071
    DatagramPacket sendPacket = new DatagramPacket(sendData,
            sendData.length, InetAddress.getByName("172.24.8.110"), 7070);
    clientSocket.send(sendPacket);

    // receive Data ==> Format:"<IP of other Client>-<Port of other Client>"
    DatagramPacket receivePacket = new DatagramPacket(new byte[1024], 1024);
    clientSocket.receive(receivePacket);

    // Convert Response to IP and Port
    String response = new String(receivePacket.getData());
    String[] splitResponse = response.split("-");
    InetAddress ip = InetAddress.getByName(splitResponse[0].substring(1));

    int port = Integer.parseInt(splitResponse[1]);

    // output converted Data for check
    System.out.println("IP: " + ip + " PORT: " + port);

    // close socket and open new socket with SAME localport
    int localPort = clientSocket.getLocalPort();
    clientSocket.close();
    clientSocket = new DatagramSocket(localPort);

    // set Timeout for receiving Data
    clientSocket.setSoTimeout(1000);

    // send 5000 Messages for testing
    for (int i = 0; i < 5000; i++) {

        // send Message to other client
        sendData = ("Datapacket(" + i + ")").getBytes();
        sendPacket = new DatagramPacket(sendData, sendData.length, ip, port);
        clientSocket.send(sendPacket);

        // receive Message from other client
        try {
            receivePacket.setData(new byte[1024]);
            clientSocket.receive(receivePacket);
            System.out.println("REC: "
                    + new String(receivePacket.getData()));

        } catch (Exception e) {
            System.out.println("SERVER TIMED OUT");
        }
    }

    // close connection
    clientSocket.close();
}

}
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2 回答 2

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与所有评论相反，您所要做的就是SO_REUSEPORT在bind().

于 2015-07-30T08:56:39.560 回答
0

看起来Java代码实际上并没有在同一个端口上打开两个套接字，而是关闭第一个套接字然后在与关闭的端口相同的端口上打开一个新的套接字。对于未处于连接状态的 UDP 套接字，根本不需要这样做。

如果您不更改端口，您的 C++ 代码应该能够继续使用相同的套接字，而不是创建一个新的。假设您想反映 Java 代码正在执行的操作，则不需要调用connect. 只需使用sendtoandrecvfrom来回发送数据。

于 2015-07-31T12:52:50.647 回答