c - 我一次可以在 TCP 套接字上写入多少字节？

Question

正如标题所说，在面向连接的套接字上一次可以写入的字节数是否有限制？

如果我想发送一个缓冲区，例如 1024 字节，我可以使用

write(tcp_socket, buffer, 1024);

或者我应该使用多个 write() 调用，每个调用的字节数较少吗？

Answer 1

write() 不保证所有字节都将被写入，因此需要多次调用 write()。来自 man write :

The number of bytes written may be less than count if, for example, there is insufficient space on the underlying physical medium, or the RLIMIT_FSIZE resource limit is encountered (see setrlimit(2)), or the call was interrupted by a signal handler after having written less than count bytes. (See also pipe(7).)

write() 返回写入的字节数，因此必须维护写入字节的运行总数并将其用作 buffer 的索引并计算剩余字节数:

ssize_t total_bytes_written = 0;
while (total_bytes_written != 1024)
{
    assert(total_bytes_written < 1024);
    ssize_t bytes_written = write(tcp_socket,
                                  &buffer[total_bytes_written],
                                  1024 - total_bytes_written);
    if (bytes_written == -1)
    {
        /* Report failure and exit. */
        break;
    }
    total_bytes_written += bytes_written;
}