.. عنوان: TCP اسٹیٹ مشین انٹرایکٹو ڈایاگرام
.. slug: tcp-state-machine
.. تاریخ: 2026-03-27 12:00:00 UTC
.. ٹیگز: نیٹ ورکنگ، ٹی سی پی، آر ایف سی 793، اسٹیٹ مشین، کیلکولیٹر، ٹول
.. زمرہ: کیلکولیٹر
.. لنک:
.. تفصیل: کلک کرنے کے قابل TCP ریاستی مشین کا خاکہ تمام RFC 793 ریاستوں کا احاطہ کرتا ہے۔ متحرک ہونے والے واقعات، پیکٹوں کا تبادلہ، ٹائمر، اور عام پھنسی ہوئی حالتوں کے لیے تشخیصی تجاویز دکھاتا ہے۔
.. قسم: متن
<style>
/* ── CANONICAL DESIGN SYSTEM ──────────────────────────────────────────────── */
.calc-container { max-width: 900px; margin: 20px auto; padding: 20px; }
.calc-header { margin-bottom: 30px; padding: 25px; background: linear-gradient(135deg, #667eea 0%, #764ba2 100%); border-radius: 12px; box-shadow: 0 4px 6px rgba(0,0,0,0.1); color: white; }
.calc-header h2 { margin-top: 0; color: white; font-size: 28px; margin-bottom: 10px; }
.calc-header p  { margin: 10px 0; opacity: 0.95; font-size: 15px; }
.result-section { background: white; border: 1px solid #e0e0e0; border-radius: 8px; margin-top: 20px; overflow: hidden; box-shadow: 0 2px 4px rgba(0,0,0,0.05); transition: all 0.3s ease; }
.result-section:hover { box-shadow: 0 4px 8px rgba(0,0,0,0.1); }
.section-header { background: linear-gradient(135deg, #4CAF50 0%, #45a049 100%); color: white; padding: 15px 20px; font-size: 18px; font-weight: bold; }
.section-content { padding: 20px; background: #fafafa; }
@media (max-width: 768px) { .calc-header h2 { font-size: 22px; } .calc-container { padding: 10px; } }
/* Page-specific */
.legend { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 16px; }
.legend-item { display: flex; align-items: center; gap: 6px; font-size: 13px; color: rgba(255,255,255,0.9); }
.legend-dot { width: 14px; height: 14px; border-radius: 50%; flex-shrink: 0; }
#cy { width: 100%; height: 520px; background: #f8faff; border-radius: 4px; }
.detail-row { display: flex; gap: 8px; margin: 6px 0; font-size: 13px; }
.detail-label { font-weight: bold; color: #2d6a2d; width: 120px; flex-shrink: 0; }
.diagnosis { background: #fff8e0; border-left: 4px solid #f0a500; padding: 10px 14px; border-radius: 6px; margin-top: 12px; font-size: 13px; }
@media (max-width: 600px) { #cy { height: 360px; } }
</style>
<div class="calc-container">
<div class="calc-header">
<h2>TCP اسٹیٹ مشین انٹرایکٹو ڈایاگرام</h2>
<p>متحرک ہونے والے واقعات، پیکٹوں کا تبادلہ، ٹائمر، اور پھنسے ہوئے ریاست کی تشخیص کی تجاویز دیکھنے کے لیے کسی بھی ریاستی نوڈ پر کلک کریں۔</p>
<div class="legend">
<div class="legend-item"><div class="legend-dot" style="background:#28a745"></div>شروع/آخری حالتیں۔</div>
<div class="legend-item"><div class="legend-dot" style="background:#4CAF50"></div>نارمل حالتیں۔</div>
<div class="legend-item"><div class="legend-dot" style="background:#dc3545"></div>TIME_WAIT / پھنس گیا۔</div>
<div class="legend-item"><div class="legend-dot" style="background:#f7971e"></div>بند ہونے والی ریاستیں۔</div>
</div>
</div>
<div class="result-section">
<div class="section-header">ریاستی خاکہ</div>
<div class="section-content" style="padding:12px">
<div id="cy"></div>
</div>
</div>
<div class="result-section" id="detailPanel">
<div class="section-header">ریاست کی تفصیلات</div>
<div class="section-content" id="detailContent">
<p style="color:#999">تفصیلات دیکھنے کے لیے اوپر ایک اسٹیٹ نوڈ پر کلک کریں۔</p>
</div>
</div>
</div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/cytoscape/3.26.0/cytoscape.min.js"></script>
<script>
const STATE_DATA = {
    CLOSED:     { color:'#28a745', event:'Initial state. No connection.',
        packet:'—', timer:'—',
        desc:'No connection exists. Starting point for both client (active open) and server (passive open).',
        diagnosis:'' },
    LISTEN:     { color:'#0f3460', event:'Server calls listen(). Waiting for SYN.',
        packet:'Receives SYN', timer:'—',
        desc:'Server is waiting for an incoming connection request.',
        diagnosis:'Stuck LISTEN: Port not open. Check: ss -lntp | grep &lt;port&gt;' },
    SYN_SENT:   { color:'#0f3460', event:'Client calls connect(). SYN sent.',
        packet:'Sends SYN', timer:'SYN-timeout (~75s)',
        desc:'Client sent SYN, waiting for SYN-ACK.',
        diagnosis:'Stuck SYN_SENT: Firewall dropping SYN, or server not listening. Check MTU/PMTUD if SYN goes out but SYN-ACK never arrives.' },
    SYN_RCVD:   { color:'#0f3460', event:'SYN received. SYN-ACK sent.',
        packet:'Receives SYN, sends SYN-ACK', timer:'SYN-backlog timer',
        desc:'Server received SYN, replied with SYN-ACK, waiting for ACK (3-way handshake).',
        diagnosis:'Many SYN_RCVD: SYN flood / DDoS. Enable tcp_syncookies: sysctl -w net.ipv4.tcp_syncookies=1' },
    ESTABLISHED:{ color:'#28a745', event:'ACK received. Connection open.',
        packet:'ACK completes handshake', timer:'Keepalive (optional, ~7200s default)',
        desc:'The normal data transfer state. Both endpoints can send and receive data.',
        diagnosis:'' },
    FIN_WAIT_1: { color:'#f7971e', event:'Application calls close(). FIN sent.',
        packet:'Sends FIN', timer:'—',
        desc:'Active closer sent FIN, waiting for ACK or FIN from peer.',
        diagnosis:'' },
    FIN_WAIT_2: { color:'#f7971e', event:'FIN-ACK received. Waiting for peer FIN.',
        packet:'Received ACK for FIN', timer:'tcp_fin_timeout (60s default)',
        desc:'ACK received for FIN, waiting for remote FIN to complete half-close.',
        diagnosis:'Stuck FIN_WAIT_2: Remote app never called close(). Reduce tcp_fin_timeout. ss -ant state fin-wait-2' },
    CLOSE_WAIT: { color:'#dc3545', event:'FIN received from peer. ACK sent.',
        packet:'Receives FIN, sends ACK', timer:'—',
        desc:'Passive closer received FIN. Waiting for local application to close().',
        diagnosis:'Many CLOSE_WAIT: Application bug — app not calling close() after receiving EOF. Profile the application for socket leaks.' },
    CLOSING:    { color:'#f7971e', event:'Both sides send FIN simultaneously.',
        packet:'FIN sent and FIN received', timer:'—',
        desc:'Simultaneous close — both sides sent FIN at same time. Rare.',
        diagnosis:'' },
    LAST_ACK:   { color:'#f7971e', event:'Passive closer sends FIN. Waiting final ACK.',
        packet:'Sends FIN', timer:'—',
        desc:'Passive closer sent its FIN, waiting for final ACK from active closer.',
        diagnosis:'' },
    TIME_WAIT:  { color:'#dc3545', event:'Final FIN received and ACKed.',
        packet:'Sends final ACK', timer:'2×MSL (60–120s, linux default 60s)',
        desc:'Waiting 2×MSL to ensure remote received the final ACK, and to prevent old segments from being accepted by a new connection.',
        diagnosis:'Many TIME_WAIT: Normal under high connection rate. Mitigate: tcp_tw_reuse=1, reduce tcp_fin_timeout, use persistent connections, or load balance across more ports.' },
};

const EDGES = [
    {from:'CLOSED',to:'LISTEN',label:'passive open\nlisten()'},
    {from:'CLOSED',to:'SYN_SENT',label:'active open\nconnect()'},
    {from:'LISTEN',to:'SYN_RCVD',label:'rcv SYN\nsnd SYN-ACK'},
    {from:'SYN_SENT',to:'ESTABLISHED',label:'rcv SYN-ACK\nsnd ACK'},
    {from:'SYN_SENT',to:'SYN_RCVD',label:'rcv SYN\n(simultaneous)'},
    {from:'SYN_RCVD',to:'ESTABLISHED',label:'rcv ACK'},
    {from:'SYN_RCVD',to:'FIN_WAIT_1',label:'close()\nsnd FIN'},
    {from:'ESTABLISHED',to:'FIN_WAIT_1',label:'close()\nsnd FIN'},
    {from:'ESTABLISHED',to:'CLOSE_WAIT',label:'rcv FIN\nsnd ACK'},
    {from:'FIN_WAIT_1',to:'FIN_WAIT_2',label:'rcv ACK'},
    {from:'FIN_WAIT_1',to:'CLOSING',label:'rcv FIN\nsnd ACK'},
    {from:'FIN_WAIT_1',to:'TIME_WAIT',label:'rcv FIN+ACK\nsnd ACK'},
    {from:'FIN_WAIT_2',to:'TIME_WAIT',label:'rcv FIN\nsnd ACK'},
    {from:'CLOSE_WAIT',to:'LAST_ACK',label:'close()\nsnd FIN'},
    {from:'CLOSING',to:'TIME_WAIT',label:'rcv ACK'},
    {from:'LAST_ACK',to:'CLOSED',label:'rcv ACK'},
    {from:'TIME_WAIT',to:'CLOSED',label:'2×MSL\ntimeout'},
];

const positions = {
    CLOSED: {x:400,y:50}, LISTEN: {x:150,y:150}, SYN_SENT: {x:650,y:150},
    SYN_RCVD: {x:150,y:280}, ESTABLISHED: {x:400,y:280},
    FIN_WAIT_1: {x:650,y:280}, CLOSE_WAIT: {x:150,y:410},
    FIN_WAIT_2: {x:650,y:410}, CLOSING: {x:500,y:410},
    LAST_ACK: {x:150,y:540}, TIME_WAIT: {x:650,y:540},
};

const cy = cytoscape({
    container: document.getElementById('cy'),
    elements: [
        ...Object.keys(STATE_DATA).map(id => ({
            data: { id, label: id.replace(/_/g,' ') },
            position: positions[id] || {x:400,y:300},
        })),
        ...EDGES.map((e,i) => ({
            data: { id:`e${i}`, source:e.from, target:e.to, label:e.label },
        })),
    ],
    style: [
        { selector: 'node', style: {
            'label': 'data(label)', 'text-wrap': 'wrap',
            'width': 110, 'height': 44,
            'shape': 'roundrectangle',
            'background-color': ele => STATE_DATA[ele.id()]?.color || '#0f3460',
            'color': '#fff', 'font-size': 11, 'font-weight': 'bold',
            'text-valign': 'center', 'text-halign': 'center',
            'border-width': 2, 'border-color': '#fff',
        }},
        { selector: 'node:selected', style: {
            'border-color': '#ffd200', 'border-width': 3,
            'box-shadow': '0 0 8px #ffd200',
        }},
        { selector: 'edge', style: {
            'label': 'data(label)', 'curve-style': 'bezier',
            'target-arrow-shape': 'triangle', 'arrow-scale': 1.2,
            'line-color': '#667', 'target-arrow-color': '#667',
            'font-size': 9, 'text-wrap': 'wrap',
            'text-background-color': '#fff', 'text-background-opacity': 0.85,
            'text-background-padding': 2,
            'color': '#333', 'width': 1.5,
        }},
    ],
    layout: { name: 'preset' },
    userZoomingEnabled: true,
    userPanningEnabled: true,
});

cy.on('tap', 'node', function(evt) {
    const id = evt.target.id();
    const d = STATE_DATA[id];
    if (!d) return;
    const diag = d.diagnosis ? `<div class="diagnosis"><strong>Diagnosis:</strong> ${d.diagnosis}</div>` : '';
    document.getElementById('detailContent').innerHTML = `
        <h3 style="margin-top: 0; color: #2d6a2d;">${id.replace(/_/g,' ')}</h3>
        <div class="detail-row"><span class="detail-label">Description:</span><span>${d.desc}</span></div>
        <div class="detail-row"><span class="detail-label">Trigger:</span><span>${d.event}</span></div>
        <div class="detail-row"><span class="detail-label">Packets:</span><span>${d.packet}</span></div>
        <div class="detail-row"><span class="detail-label">Timer:</span><span>${d.timer}</span></div>
        ${diag}`;
});

cy.fit(cy.nodes(), 30);
</script>