MODBUS_TCP_ACCEPT(3)

💖 MODBUS_TCP_ACCEPT 💖

okay bestie, welcome to the libmodbus Manual, section 3 ✨ this is the page for modbus_tcp_accept, aka the glow-up moment where your TCP Modbus server (IPv4 edition 🌈) finally lets a client in the door.

---

🌸 NAME 🌸

modbus_tcp_accept — accept a new connection on a TCP Modbus socket (IPv4) 🫶

---

✨ SYNOPSIS ✨

int modbus_tcp_accept(modbus_t *ctx, int *'s);

---

💅 DESCRIPTION 💅

so like. the modbus_tcp_accept() function shall extract the first connection on the queue of pending connections, create a brand new socket, and store it in the libmodbus context you handed it as an argument. main character behaviour, honestly 👑

and listen — if it's available, accept4() with SOCK_CLOEXEC will be called instead of accept(). fancy ✨ iykyk.

---

🎀 RETURN VALUE 🎀

success? you get a new socket back. slay 💚

not success? it shall return -1 and set errno. 😭 it's giving error handling.

---

🦋 EXAMPLE 🦋

for the detailed example, go look at the unit-test-server.c source file in the tests directory 👀

...

ctx = modbus_new_tcp("127.0.0.1", 502);
s = modbus_tcp_listen(ctx, 1);
modbus_tcp_accept(ctx, &s);

...

close(s)
modbus_free(ctx);

look at that flow. setup, listen, accept, cleanup. the way that it just works. periodt 💅

---

🌟 SEE ALSO 🌟

• modbus_tcp_pi_accept(3)
• modbus_tcp_listen(3)
• modbus_tcp_pi_listen(3)

---

👑 AUTHORS 👑

the libmodbus documentation was written by Stéphane Raimbault <stephane.raimbault@gmail.com> 💜

---

aaaand that's the page!! this was libmodbus v3.1.6, dated 11/17/2025 — mwah, no notes, go accept some connections bestie 🫶✨💖