.. tiêu đề: Sơ đồ tương tác máy trạng thái TCP
.. sên: tcp-state-machine
.. ngày: 27-03-2026 12:00:00 UTC
.. tags: mạng, tcp, rfc793, máy trạng thái, máy tính, công cụ
.. thể loại: Máy tính
.. liên kết:
.. mô tả: Sơ đồ máy trạng thái TCP có thể nhấp bao gồm tất cả các trạng thái RFC 793. Hiển thị các sự kiện kích hoạt, gói được trao đổi, bộ hẹn giờ và mẹo chẩn đoán cho các trạng thái bị kẹt phổ biến.
.. loại: văn bản
<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>Sơ đồ tương tác máy trạng thái TCP</h2>
<p>Nhấp vào bất kỳ nút trạng thái nào để xem các sự kiện kích hoạt, các gói được trao đổi, bộ hẹn giờ và mẹo chẩn đoán trạng thái bị kẹt.</p>
<div class="legend">
<div class="legend-item"><div class="legend-dot" style="background:#28a745"></div>Trạng thái bắt đầu/kết thúc</div>
<div class="legend-item"><div class="legend-dot" style="background:#4CAF50"></div>Trạng thái bình thường</div>
<div class="legend-item"><div class="legend-dot" style="background:#dc3545"></div>TIME_WAIT / bị kẹt</div>
<div class="legend-item"><div class="legend-dot" style="background:#f7971e"></div>Trạng thái đóng cửa</div>
</div>
</div>
<div class="result-section">
<div class="section-header">Sơ đồ trạng thái</div>
<div class="section-content" style="padding:12px">
<div id="cy"></div>
</div>
</div>
<div class="result-section" id="detailPanel">
<div class="section-header">Chi tiết tiểu bang</div>
<div class="section-content" id="detailContent">
<p style="color:#999">Nhấp vào nút trạng thái ở trên để xem chi tiết.</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>