Question

我试图更好地了解Perl，并且发现了有关套接字的问题。我试着理解一个简单的＆＃34;我在xmodulo找到的例子。我期待像在示例中端口将是7777.但似乎用于此套接字通信的端口大约在35000以上并且在客户端脚本的每次调用中端口增加+1。为什么端口与7777不同？为什么它在每次通话时递增？

服务器示例如下所示：

use IO::Socket::INET;     
# auto-flush on socket
$| = 1;     
# creating a listening socket
my $socket = new IO::Socket::INET (
    LocalHost => '0.0.0.0',
    LocalPort => '7777',
    Proto => 'tcp',
    Listen => 5,
    Reuse => 1
);
die "cannot create socket $!\n" unless $socket;
print "server waiting for client connection on port 7777\n";

while(1)
{
    # waiting for a new client connection
    my $client_socket = $socket->accept();

    # get information about a newly connected client
    my $client_address = $client_socket->peerhost();
    my $client_port = $client_socket->peerport();
    print "connection from $client_address:$client_port\n";

    # read up to 1024 characters from the connected client
    my $data = "";
    $client_socket->recv($data, 1024);
    print "received data: $data\n";

    # write response data to the connected client
    $data = "ok";
    $client_socket->send($data);

    # notify client that response has been sent
    shutdown($client_socket, 1);
}

$socket->close();

客户端示例是：

use IO::Socket::INET;     
# auto-flush on socket
$| = 1;

# create a connecting socket
my $socket = new IO::Socket::INET (
    PeerHost => '192.168.1.10',
    PeerPort => '7777',
    Proto => 'tcp',
);
die "cannot connect to the server $!\n" unless $socket;
print "connected to the server\n";

# data to send to a server
my $req = 'hello world';
my $size = $socket->send($req);
print "sent data of length $size\n";

# notify server that request has been sent
shutdown($socket, 1);

# receive a response of up to 1024 characters from server
my $response = "";
$socket->recv($response, 1024);
print "received response: $response\n";

$socket->close();

Answer 1

连接不是由

定义的

当地地址
同行地址
端口

由

定义

当地地址
本地端口
同行地址
peer port

例如，

>netstat /a

Active Connections

  Proto  Local Address          Foreign Address        State
  ...
  TCP    10.0.0.2:34208         stackoverflow:http     ESTABLISHED
  TCP    10.0.0.2:34212         stackoverflow:http     ESTABLISHED
  TCP    10.0.0.2:34213         stackoverflow:http     ESTABLISHED
  TCP    10.0.0.2:34224         stackoverflow:http     ESTABLISHED
  TCP    10.0.0.2:34226         stackoverflow:http     ESTABLISHED
  TCP    10.0.0.2:34227         stackoverflow:http     ESTABLISHED
  ...

您没有为客户端指定本地端口，因此系统选择了一个可用的端口。这是正确的做法。没有理由将客户端限制为一个端口。它甚至可能导致问题。

例如，假设您的网络浏览器尝试bind其套接字到端口80（Web服务器listen上的端口）。您的网络浏览器一次只能有一个待处理的请求。那会很糟糕。您希望能够创建到同一服务的多个连接。这允许您同时请求两个不同的图像，这允许您同时在两个不同的选项卡中加载两个页面，依此类推。在上面的示例中，我的计算机有六个连接到stackoverflow.com的端口80，但如果Web浏览器已将套接字绑定到端口80，则无法实现。

IO :: SOCKET :: INET上的端口跳跃

1 个答案: