.. शीर्षक: टीसीपी स्टेट मशीन इंटरैक्टिव आरेख
.. स्लग: टीसीपी-स्टेट-मशीन
.. दिनांक: 2026-03-27 12:00:00 यूटीसी
.. टैग: नेटवर्किंग, टीसीपी, आरएफसी793, स्टेट-मशीन, कैलकुलेटर, टूल
.. श्रेणी: कैलकुलेटर
.. लिंक:
.. विवरण: क्लिक करने योग्य टीसीपी राज्य मशीन आरेख सभी आरएफसी 793 राज्यों को कवर करता है। सामान्य अटके हुए राज्यों के लिए ट्रिगरिंग इवेंट, एक्सचेंज किए गए पैकेट, टाइमर और निदान युक्तियाँ दिखाता है।
.. प्रकार: पाठ
<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>टीसीपी स्टेट मशीन इंटरैक्टिव आरेख</h2>
<p>ट्रिगरिंग इवेंट, एक्सचेंज किए गए पैकेट, टाइमर और अटके हुए राज्य निदान युक्तियाँ देखने के लिए किसी भी राज्य नोड पर क्लिक करें।</p>
<div class="legend">
<div class="legend-item"><div class="legend-dot" style="background:#28a745"></div>आरंभ/समाप्ति स्थितियाँ</div>
<div class="legend-item"><div class="legend-dot" style="background:#4CAF50"></div>सामान्य अवस्थाएँ</div>
<div class="legend-item"><div class="legend-dot" style="background:#dc3545"></div>TIME_WAIT / अटक गया</div>
<div class="legend-item"><div class="legend-dot" style="background:#f7971e"></div>समापन अवस्थाएँ</div>
</div>
</div>
<div class="result-section">
<div class="section-header">राज्य आरेख</div>
<div class="section-content" style="padding:12px">
<div id="cy"></div>
</div>
</div>
<div class="result-section" id="detailPanel">
<div class="section-header">राज्य विवरण</div>
<div class="section-content" id="detailContent">
<p style="color:#999">विवरण देखने के लिए ऊपर एक राज्य नोड पर क्लिक करें।</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>