c - How to open the two udp client socket with same local port -

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how open 2 client socket same local port java. in java can mention source port while creating datagrampacket. trying udp hole punching. correct me if done wrong.

i have added code here.

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 message if ( sendto ( s , message , strlen(message) , 0 , (struct sockaddr *) &si_other , slen ) == socket_error) {     printf ( "sendto() failed error code : %d" , wsagetlasterror() ) ;    return ; }  //receive reply , print memset ( buf , '\0' , buflen ) ; //try receive data, blocking call if ( recvfrom ( s , buf , buflen , 0 , (struct sockaddr *) &si_other , &slen ) == socket_error ) {     printf("recvfrom() failed 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, 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 ( ) ;

}

in same method trying open new socket same port.

check java code trying in c/c++. not possible ??

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 server 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 ip , 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 check     system.out.println("ip: " + ip + " port: " + port);      // close socket , open new socket same localport     int localport = clientsocket.getlocalport();     clientsocket.close();     clientsocket = new datagramsocket(localport);      // set timeout receiving data     clientsocket.setsotimeout(1000);      // send 5000 messages testing     (int = 0; < 5000; i++) {          // send message other client         senddata = ("datapacket(" + + ")").getbytes();         sendpacket = new datagrampacket(senddata, senddata.length, ip, port);         clientsocket.send(sendpacket);          // receive message 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(); }  }

contrary commentary, have set socket option so_reuseport prior bind().


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