这与以下问题有关: SCTP with Multihoming as a Drop In Replacement for TCP
我有一个简单的回显客户端/并发服务器应用程序,它使用 TCP 运行得非常好。我可以通过管道将文件传输到客户端上的标准输入,客户端将接收所有数据,调用select
将返回 1 指示套接字是可读的,然后对 read 的调用将返回 0 指示 EOF / FIN。然后客户端将退出。一切都很好。
但是,SCTP 上的相同应用程序会导致问题。所做的唯一更改是从 IPPROTO_TCP 到 IPPROTO_SCTP。服务器分叉,回显数据,孩子退出并由父母收割。客户端接收到所有数据,但之后select
不断返回 0 个准备就绪的描述符(如果没有我添加的超时,它将永远挂起)。
世界上到底发生了什么?
这是客户端的代码:
#!/usr/bin/perl -w
use strict;
use Socket;
# forward declaration
sub logmsg;
my $remote = shift || "localhost";
my $port = 9877;
($port) = $port =~ /^(\d+)$/ or die "invalid port";
my $iaddr = inet_aton($remote) || die "no host: $remote";
my $paddr = sockaddr_in($port, $iaddr);
my $proto = getprotobyname('sctp');
my $sockfd;
socket($sockfd, PF_INET, SOCK_STREAM, $proto) || die "socket: $!";
connect($sockfd, $paddr) || die "connect: $!";
str_cli($sockfd);
exit(0);
#----- subs down here ------#
sub str_cli {
my $sockfd = shift;
my ($n, $buff, $stdineof, $s);
my $rin = '';
$stdineof = 0;
while ( 1 ) {
if ($stdineof == 0) {
vec($rin, fileno(STDIN), 1) = 1;
}
vec($rin, fileno($sockfd), 1) = 1;
my $nfound = select($rin, undef, undef, 1.0);
if ($nfound < 0) {
next if $!{EINTR};
die "select: $!";
} else { print "\$nfound == $nfound\n"; }
if (vec($rin, fileno($sockfd), 1) == 1) { # socket readable
print "trying to read from sockfd\n";
$n = sysread($sockfd, $buff, 1024);
if (!defined($n) || $n < 0) {
# resume if sysread() returned because a signal was received
next if $!{EINTR};
die "sysread: $!";
} elsif($n == 0) {
if ($stdineof == 1) { return; } # normal termination
else { die "str_cli: server terminated prematurely"; }
}
writen(*STDOUT, $buff);
}
if (vec($rin, fileno(STDIN), 1) == 1) { # stdin readable
$n = sysread(STDIN, $buff, 1024);
if (!defined($n) || $n < 0) {
# resume if sysread() returned because a signal was received
next if $!{EINTR};
die "sysread: $!";
} elsif($n == 0) {
$stdineof = 1;
if (!defined($s = shutdown($sockfd, SHUT_WR))
|| $s == 0) { die("shutdown: $!"); }
vec($rin, fileno(STDIN), 1) = 0;
next;
}
writen($sockfd, $buff);
}
}
}
sub writen {
my ($connfd, $buff) = @_;
my $nleft = length($buff);
my $total = 0;
my $nwritten = 0;
while ($nleft) {
if (($nwritten = syswrite($connfd, $buff, $nleft, $total)) <= 0) {
# resume if syswrite() returned because a signal was received
# 0 indicates an error in this context
next if $!{EINTR};
die "syswrite: $!";
}
$nleft -= $nwritten;
$total += $nwritten;
}
}
sub logmsg { print "$0 $$: @_ at ", scalar localtime, "\n" }
请记住,这可以通过 TCP 完美运行。我在 Ubuntu 9.04 上安装了所有需要的 sctp 包。