java - Perl 客户端到 Java 服务器

Question

我正在尝试编写一个 Perl 客户端程序来连接到 Java 服务器应用程序 (JDuplicate)。我看到 java 服务器使用 DataInput.readUTF 和 DataInput.writeUTF 方法，JDuplicate 网站将其列为“Java 的修改版 UTF-8 协议(protocol)”。

我的测试程序非常简单，我正在尝试发送客户端类型数据，这应该调用服务器的响应，但它只是超时:

#!/usr/bin/perluse strict;use Encode;use IO::Socket;my $remote = IO::Socket::INET->new(  Proto => 'tcp',  PeerAddr => 'localhost',  PeerPort => '10421') or die "Cannot connect to server\n";$|++;$remote->send(encode_utf8("CLIENTTYPE|JDSC#0.5.9#0.2"));while (<$remote>) {  print $_,"\n";}close($remote);exit(0);

我尝试过 $remote->send(pack("U","..."));，我尝试过“use utf8;”，我尝试过 binmode($remote, ":utf8 ")，并且我尝试仅发送纯 ASCII 文本，但没有得到任何响应。

我可以看到使用 tcpdump 发送的数据，全部在一个数据包中，但服务器本身不对其执行任何操作(除了确认数据包)。

我需要做一些额外的事情来满足Java的“修改的”utf实现吗？

谢谢。

Answer 1

您必须实现 protocol正确的是:

First, the total number of bytes needed to represent all the characters of s is calculated. If this number is larger than 65535, then a UTFDataFormatException is thrown. Otherwise, this length is written to the output stream in exactly the manner of the writeShort method; after this, the one-, two-, or three-byte representation of each character in the string s is written.

如 writeShort 文档中所示，它按网络顺序发送 16 位数量。

在 Perl 中，这类似于

sub sendmsg {
  my($s,$msg) = @_;

  die "message too long" if length($msg) > 0xffff;

  my $sent = $s->send(
    pack(n => (length($msg) & 0xffff)) .
    $msg
  );

  die "send: $!"    unless defined $sent;
  die "short write" unless $sent == length($msg) + 2;
}

sub readmsg {
  my($s) = @_;
  my $buf;
  my $nread;

  $nread = $s->read($buf, 2);
  die "read: $!"   unless defined $nread;
  die "short read" unless $nread == 2;

  my $len = unpack n => $buf;

  $nread = $s->read($buf, $len);
  die "read: $!"   unless defined $nread;
  die "short read" unless $nread == $len;

  $buf;
}

尽管上面的代码不执行修改后的 UTF 编码，但它会引发响应:

my $remote = IO::Socket::INET->new(
  Proto => 'tcp',
  PeerAddr => 'localhost',
  PeerPort => '10421'
) or die "Cannot connect to server: $@\n";

my $msg = "CLIENTTYPE|JDSC#0.5.9#0.2";

sendmsg $remote, $msg;

my $buf = readmsg $remote;
print "[$buf]\n";

输出:

[SERVERTYPE|JDuplicate#0.5.9 beta (build 584)#0.2]