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<b>14.</b>
TCP/IP Internetworking
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<h1 id="tcpip-internetworking">TCP/IP Internetworking</h1>
<p>bash shell 에서 특정 주소 형식을 이용해 socket 연결 기능을 제공하는 것처럼
awk 에서도 아래와 같은 주소 형식의 스트링을 사용하면 자동으로 socket 연결로 인식합니다.
서버쪽 주소는 localport 를 알맞은 값으로 적어주면 되고 hostname 과 remoteport 는 0
으로 두면 됩니다.
클라이언트 주소는 localport 를 0 으로 두고 연결할 hostname 과 remoteport 를 알맞게 설정하면 됩니다.
hostname 은 ip 주소로도 사용할 수 있습니다.</p>
<p><img src="images/tcp_ip_uri.png" alt=""></p>
<blockquote>
<ul>
<li>net-type : /inet4/ 는 IPv4, /inet6/ 는 IPv6, /inet/ 는 system default </li>
<li>protocol : tcp 또는 udp</li>
</ul>
</blockquote>
<p>송신만 하거나 수신만 하는 단방향일 경우는 redirection ( <code><</code>, <code>></code> ) 을 사용할 수 있지만
양방향 통신일 경우는 coprocess ( <code>|&</code> ) 를 사용해야 합니다.
파이프로 두 개의 외부 명령을 직접 연결해 사용할 수 없듯이
socket 도 직접 외부 명령을 연결해 사용할 수 없습니다.</p>
<pre><code class="lang-bash">$ awk -b <span class="hljs-string">'BEGIN{
"cat file1" |& "/inet/tcp/0/some.host.com/8080"
}'</span>
awk: cmd. line:<span class="hljs-number">2</span>: <span class="hljs-string">"cat file1"</span> |& <span class="hljs-string">"/inet/tcp/0/some.host.com/8080"</span>
awk: cmd. line:<span class="hljs-number">2</span>: ^ syntax error
</code></pre>
<h3 id="임시-웹-서버">임시 웹 서버</h3>
<p>디렉토리에 <a href="examples/webserver.awk">webserver.awk</a> 와 <a href="examples/cat.jpg">cat.jpg</a>
파일을 복사한 후 <code>awk -f webserver.awk</code> 로 실행하면 됩니다.</p>
<blockquote>
<p>각 리소스 ( html, image ) 별로 download 를 위해 tcp 연결을 맺고 끊는 http/1.0 방식입니다.</p>
</blockquote>
<pre><code class="lang-bash">@load <span class="hljs-string">"filefuncs"</span>
@load <span class="hljs-string">"readfile"</span>
BEGIN {
RS = ORS = <span class="hljs-string">"\r\n"</span>
datefmt = <span class="hljs-string">"Date: %a, %d %b %Y %H:%M:%S %Z"</span>
socket = <span class="hljs-string">"/inet/tcp/8080/0/0"</span>
<span class="hljs-keyword">while</span> (socket |& getline > <span class="hljs-number">0</span>) {
<span class="hljs-keyword">if</span> ( <span class="hljs-variable">$1</span> == <span class="hljs-string">"GET"</span> ) {
<span class="hljs-built_in">print</span> <span class="hljs-string">"GET : "</span>, <span class="hljs-variable">$2</span>
<span class="hljs-variable">$2</span> = substr(<span class="hljs-variable">$2</span>,<span class="hljs-number">2</span>)
switch (<span class="hljs-variable">$2</span>) {
<span class="hljs-keyword">case</span> /\.(jpg|gif|png)$/ :
sendImage(<span class="hljs-variable">$2</span>)
<span class="hljs-built_in">break</span>
default :
sendHtml()
}
}
}
}
<span class="hljs-keyword">function</span> sendHtml( a, arr) {
arr[<span class="hljs-string">"type"</span>] = <span class="hljs-string">"text/html"</span>
arr[<span class="hljs-string">"content"</span>] = <span class="hljs-string">"\
<HTML>\n\
<HEAD><TITLE>Out Of Service</TITLE></HEAD>\n\
<BODY>\n\
<H1>This site is temporarily out of service.</H1>\n\
<P><img src=cat.jpg></P>\n\
</BODY>\n\
</HTML>\n\
"</span>
arr[<span class="hljs-string">"length"</span>] = length(arr[<span class="hljs-string">"content"</span>])
arr[<span class="hljs-string">"date"</span>] = strftime(datefmt, systime(), <span class="hljs-number">1</span>)
send(arr)
}
<span class="hljs-keyword">function</span> sendImage(file, cmd, a, arr, <span class="hljs-built_in">type</span>) {
RS=<span class="hljs-string">"\n"</span>
cmd = <span class="hljs-string">"file -b --mime-type '"</span> file <span class="hljs-string">"'"</span>
cmd | getline <span class="hljs-built_in">type</span>; close(cmd)
RS=<span class="hljs-string">"\r\n"</span>
arr[<span class="hljs-string">"type"</span>] = <span class="hljs-built_in">type</span>
<span class="hljs-built_in">stat</span>(file, a)
arr[<span class="hljs-string">"length"</span>] = a[<span class="hljs-string">"size"</span>]
arr[<span class="hljs-string">"content"</span>] = readfile(file)
arr[<span class="hljs-string">"date"</span>] = strftime(datefmt, systime(), <span class="hljs-number">1</span>)
send(arr)
}
<span class="hljs-keyword">function</span> send(arr) {
<span class="hljs-built_in">print</span> <span class="hljs-string">"HTTP/1.0 200 OK"</span> |& socket
<span class="hljs-built_in">print</span> arr[<span class="hljs-string">"date"</span>] |& socket
<span class="hljs-built_in">print</span> <span class="hljs-string">"Server: AWK"</span> |& socket
<span class="hljs-built_in">print</span> <span class="hljs-string">"Content-Length: "</span> arr[<span class="hljs-string">"length"</span>] |& socket
<span class="hljs-built_in">print</span> <span class="hljs-string">"Content-Type: "</span> arr[<span class="hljs-string">"type"</span>] |& socket
<span class="hljs-built_in">print</span> <span class="hljs-string">""</span> |& socket
<span class="hljs-built_in">print</span> arr[<span class="hljs-string">"content"</span>] |& socket
<span class="hljs-built_in">print</span> <span class="hljs-string">"close socket"</span>
close(socket)
}
</code></pre>
<p><a name="chat"></a></p>
<h3 id="양방향-채팅">양방향 채팅</h3>
<p>위에서 작성한 웹 서버의 경우는 메시지가 전송되는 순서가 request, response 로 일정하기 때문에
하나의 프로세스로도 처리할 수가 있었는데요.
양방향 채팅의 경우는 일정한 순서 없이 임의로 전달되기 때문에
입력과 출력을 따로 처리해줘야 되므로 두 개의 프로세스가 필요합니다.</p>
<p>fork 하기 전에 server 의 <code>socket |& getline</code> 와 client 의 <code>print "" |& socket</code> 로
먼저 socket 을 연결하는 것은 child 와 parent 프로세스가 동일한 socket 을 사용하기 위해서입니다.
상대방이 종료하게 되면 socket 에 연결 중인 parent 프로세스만 종료되고
child 프로세스는 남게 되므로 종료전에 먼저 kill 외부 명령으로 child pid 를 종료시킵니다.</p>
<blockquote>
<p>한가지 주의할 것은 heredoc 으로 작성하면 안되고 quotes 이나 파일로 만들어서 실행해야 됩니다.</p>
</blockquote>
<p><img src="images/tcp_ip_fork.png" alt=""></p>
<pre><code class="lang-bash"><span class="hljs-comment">############ 먼저 server 를 실행 ############</span>
$ awk <span class="hljs-string">'
@load "fork"
BEGIN{
socket = "/inet/tcp/8080/0/0"
socket |& getline
if (( pid = fork() ) == 0 ) {
while (getline msg < "/dev/stdin" > 0) # child
print msg |& socket
} else {
while (socket |& getline msg > 0) # parent
print msg
system("kill " pid)
}
}'</span>
<span class="hljs-comment">############## chat client ##############</span>
$ awk <span class="hljs-string">'
@load "fork"
BEGIN{
socket = "/inet/tcp/0/some.host.com/8080" # localhost or 0.0.0.0
print "" |& socket
if (( pid = fork() ) == 0 ) {
while (getline msg < "/dev/stdin" > 0) # child
print msg |& socket
} else {
while (socket |& getline msg > 0) # parent
print msg
system("kill " pid)
}
}'</span>
</code></pre>
<h3 id="바이너리-파일-전송">바이너리 파일 전송</h3>
<p>awk 는 기본적으로 텍스트 데이터를 다루는 프로그램이지만
약간 다른 방식으로 활용을 하여 바이너리 파일 전송을 구현한 것입니다.
이때는 입출력 데이터를 byte 로 다루는 <code>-b</code> 옵션을 사용해야 하고
RS 설정과 RT 변수를 활용합니다.</p>
<blockquote>
<p>테스트에 사용한 gawk 버전이 4.1.4 인데 구버전의 경우 정상적으로 작동하지 않을 수 있습니다.</p>
</blockquote>
<p><code>RS=".{1,3}"</code> 형식을 이용하여 일정한 크기로 데이터 읽어들이기 예제</p>
<pre><code class="lang-bash">$ <span class="hljs-built_in">echo</span> -n <span class="hljs-number">0123456789</span> |
awk <span class="hljs-string">'{ printf "NR:%s, NF:%s, $0:(%s), RT:(%s)\n", NR, NF, $0, RT }'</span> RS=<span class="hljs-string">'.{1,3}'</span>
NR:<span class="hljs-number">1</span>, NF:<span class="hljs-number">0</span>, <span class="hljs-variable">$0</span>:(), RT:(<span class="hljs-number">012</span>)
NR:<span class="hljs-number">2</span>, NF:<span class="hljs-number">0</span>, <span class="hljs-variable">$0</span>:(), RT:(<span class="hljs-number">345</span>)
NR:<span class="hljs-number">3</span>, NF:<span class="hljs-number">0</span>, <span class="hljs-variable">$0</span>:(), RT:(<span class="hljs-number">678</span>)
NR:<span class="hljs-number">4</span>, NF:<span class="hljs-number">0</span>, <span class="hljs-variable">$0</span>:(), RT:(<span class="hljs-number">9</span>)
</code></pre>
<p>바이너리 파일 전송</p>
<pre><code class="lang-bash"><span class="hljs-comment">################# file receiver #################</span>
$ awk -b <span class="hljs-operator">-f</span> - <<\EOF
BEGIN{ RS=<span class="hljs-string">".{1,300}"</span>
<span class="hljs-keyword">while</span> ( getline < <span class="hljs-string">"/inet/tcp/8080/0/0"</span> > <span class="hljs-number">0</span> ) {
<span class="hljs-built_in">printf</span> <span class="hljs-string">"%s"</span>, RT > <span class="hljs-string">"file1.jpg.copy"</span>
sum += length(RT)
<span class="hljs-built_in">printf</span> <span class="hljs-string">"\r%'d bytes received"</span>, sum
}
<span class="hljs-built_in">print</span> <span class="hljs-string">""</span>
}
EOF
<span class="hljs-number">1</span>,<span class="hljs-number">637</span>,<span class="hljs-number">568</span> bytes received
<span class="hljs-comment">################## file sender ###################</span>
$ awk -b <span class="hljs-operator">-f</span> - <<\EOF
BEGIN{ RS=<span class="hljs-string">".{1,300}"</span>
<span class="hljs-keyword">while</span> ( getline < <span class="hljs-string">"file1.jpg"</span> > <span class="hljs-number">0</span> ) {
<span class="hljs-built_in">printf</span> <span class="hljs-string">"%s"</span>, RT > <span class="hljs-string">"/inet/tcp/0/some.host.com/8080"</span>
sum += length(RT)
<span class="hljs-built_in">printf</span> <span class="hljs-string">"\r%'d bytes sent"</span>, sum
}
<span class="hljs-built_in">print</span> <span class="hljs-string">""</span>
}
EOF
<span class="hljs-number">1</span>,<span class="hljs-number">637</span>,<span class="hljs-number">568</span> bytes sent
</code></pre>
<p>tar 파일 전송</p>
<pre><code class="lang-bash"><span class="hljs-comment">############### tar receiver ################</span>
$ awk -b <span class="hljs-string">'BEGIN{ RS=".{1,300}"
while ( getline < "/inet/tcp/8080/0/0" > 0 ) {
printf "%s", RT | "tar xvz"
}
}'</span>
<span class="hljs-comment">############### tar sender ##################</span>
$ awk -b <span class="hljs-string">'BEGIN{ RS=".{1,300}"
while ( "tar cvz ./mydir" | getline ) {
printf "%s", RT > "/inet/tcp/0/some.host.com/8080"
}
}'</span>
</code></pre>
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