MODBUS_SET_SOCKET(3)

💖 MODBUS_SET_SOCKET 💖

okay bestie, welcome to modbus_set_socket(3) from the libmodbus Manual — yes we're in section 3, we're in the library pages, we're thriving ✨

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🌸 NAME 🌸

modbus_set_socket — set socket of the context 🧦

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🎀 SYNOPSIS 🎀

int modbus_set_socket(modbus_t *ctx, int s);

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✨ DESCRIPTION ✨

okay so. the modbus_set_socket() function shall set the socket or file descriptor inside the libmodbus context. that's it, that's the whole job, and she does it flawlessly 💅

the way this is genuinely useful is when you're out here managing multiple client connections to the same server — like, one context, many sockets, rotating through them like it's nothing. main character energy fr fr 👑

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🦋 RETURN VALUE 🦋

the function shall return 0 if it's successful. otherwise it shall return -1 and set errno — so like, check your errno, she's trying to tell you something 😭

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🌈 EXAMPLE 🌈

here's the vibe, look at her go:

ctx = modbus_new_tcp("127.0.0.1", 1502);
server_socket = modbus_tcp_listen(ctx, NB_CONNECTION);

FD_ZERO(&rdset);
FD_SET(server_socket, &rdset);

/* .... */

if (FD_ISSET(master_socket, &rdset)) {
    modbus_set_socket(ctx, master_socket);
    rc = modbus_receive(ctx, query);
    if (rc != -1) {
        modbus_reply(ctx, query, rc, mb_mapping);
    }
}

see how she swaps the socket in with modbus_set_socket(ctx, master_socket) right before receiving? that's the moment. ate, no crumbs 🍓

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👀 SEE ALSO 👀

• modbus_get_socket(3) — the other half of the duo, the getter to this setter, iykyk 💜

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🫶 AUTHORS 🫶

the libmodbus documentation was written by Stéphane Raimbault <stephane.raimbault@gmail.com> — thank you king, we love the docs 🌸

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and that's the whole page bestie!! this was libmodbus v3.1.6, dated 11/17/2025, and she's still iconic. go set that socket, you got this 💖✨🎀🦋