setsockopt SO_REUSEADDR

[Rainer Hochreiter]

running the program listed below with argument 'reuse' under cygwin and
linux returns different results!

from my point of view, the linux result is quite what i expected, a bind()
error 'Address already in use'. why doen't bind() return an error under
cygwin?

running under cygwin:

~$ ./tcptest.cygwin.exe reuse &
using socket=4200064
setsockopt(SO_REUSEADDR)

~$ ./tcptest.cygwin.exe reuse
using socket=4200064
setsockopt(SO_REUSEADDR)

running under linux:

~$ ./tcptest.linux reuse &
using socket=134513784
setsockopt(SO_REUSEADDR)

~$ ./tcptest.linux reuse
using socket=134513784
setsockopt(SO_REUSEADDR)
bind() failed: Address already in use

#-----------------------------------------------------------------

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

int main(int argc, char** argv)
{
  const unsigned reuse = (argc == 2 && strcmp(argv[1], "reuse") == 0);
  int s = -1;
  if ((s = socket(AF_INET, SOCK_STREAM, 0)) < 0)
    {
      perror("socket() failed");
      exit(1);
    }
  printf("using socket=%d\n", socket);

  if (reuse)
    {
      int on = 1;
      printf("setsockopt(SO_REUSEADDR)\n");
      if (setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
        {
          perror("setsockopt(SO_REUSEADDR) failed");
        }
    }

  struct sockaddr_in saddr;
  bzero((char *) &saddr, sizeof(saddr));
  saddr.sin_family      = AF_INET;
  saddr.sin_addr.s_addr = htonl(INADDR_ANY);
  saddr.sin_port        = htons(12345);

  if (bind(s, (struct sockaddr *) &saddr, sizeof(saddr)) < 0)
    {
      perror("bind() failed");
      exit(1);
    }

  listen(s, 5);

  while (1)
    {
      struct sockaddr_in caddr;
      int caddr_len = sizeof(caddr);
      int s2;
      if ((s2 = accept(s, (struct sockaddr *) &caddr, &caddr_len)) < 0)
        {
          perror("accept() failed");
          exit(1);
        }
      close(s2);
    }

  return 0;
}



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