.. título: Diagrama interactivo de la máquina de estados TCP
.. babosa: tcp-estado-máquina
.. fecha: 2026-03-27 12:00:00 UTC
.. etiquetas: redes, tcp, rfc793, máquina de estado, calculadora, herramienta
.. categoría: Calculadoras
.. enlace:
.. description: Clickable TCP state machine diagram covering all RFC 793 states. Muestra eventos desencadenantes, paquetes intercambiados, temporizadores y consejos de diagnóstico para estados de bloqueo comunes.
.. tipo: texto
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@media (max-width: 600px) { #cy { height: 360px; } }
</style>
<div class="calc-container">
<div class="calc-header">
<h2>Diagrama interactivo de la máquina de estados TCP</h2>
<p>Haga clic en cualquier nodo de estado para ver eventos desencadenantes, paquetes intercambiados, temporizadores y sugerencias de diagnóstico de estados bloqueados.</p>
<div class="legend">
<div class="legend-item"><div class="legend-dot" style="background:#28a745"></div>Estados de inicio/fin</div>
<div class="legend-item"><div class="legend-dot" style="background:#4CAF50"></div>Estados normales</div>
<div class="legend-item"><div class="legend-dot" style="background:#dc3545"></div>TIME_WAIT / atascado</div>
<div class="legend-item"><div class="legend-dot" style="background:#f7971e"></div>Estados de cierre</div>
</div>
</div>
<div class="result-section">
<div class="section-header">Diagrama de estado</div>
<div class="section-content" style="padding:12px">
<div id="cy"></div>
</div>
</div>
<div class="result-section" id="detailPanel">
<div class="section-header">Detalles del estado</div>
<div class="section-content" id="detailContent">
<p style="color:#999">Haga clic en un nodo de estado arriba para ver detalles.</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 },
        })),
    ],
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            'width': 110, 'height': 44,
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            'font-size': 9, 'text-wrap': 'wrap',
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            '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>