TCPSocket.write method | Bun module | Bun

Writes data to the socket. This method is unbuffered and non-blocking. This uses the sendto(2) syscall internally.

For optimal performance with multiple small writes, consider batching multiple writes together into a single socket.write() call.

The data to write. Can be a string (encoded as UTF-8), ArrayBuffer, TypedArray, or DataView.

The offset in bytes within the buffer to start writing from. Defaults to 0. Ignored for strings.

The number of bytes to write from the buffer. Defaults to the remaining length of the buffer from the offset. Ignored for strings.

The number of bytes written. Returns -1 if the socket is closed or shutting down. Can return less than the input size if the socket's buffer is full (backpressure).

// Send a string
const bytesWritten = socket.write("Hello, world!\n");

// Send binary data
const buffer = new Uint8Array([0x01, 0x02, 0x03]);
socket.write(buffer);

// Send part of a buffer
const largeBuffer = new Uint8Array(1024);
// ... fill largeBuffer ...
socket.write(largeBuffer, 100, 50); // Write 50 bytes starting from index 100