Most efficient way to send one byte op-code between processes (IPC)?

I have two processes (one in C and another in Python) that comunicate between them by sending 1-byte OP codes.

I was using sockets (AF_UNIX, SOCK_STREAM), however, when I was looking into the Sockets buffer I saw :

ss -nx | grep 145115781

u_str ESTAB 0 768 my_socket 145253942 *145115781
u_str ESTAB 1 0 * 145115781 *145253942

as you can see the Send-Q of the socket is 768 even though I have sent 1 byte (the only explanation to it I found here) it looks not efficient to send 768 bytes buffer for effective data of one byte.

what is the best way to do it? and if you have a better explanation for the 768 bytes I would be glad to here is.

server:

        struct sockaddr_un local;
        int len;

        if((server_sockfd = socket(AF_UNIX, SOCK_STREAM, 0)) == -1)
        {
                perror("Error creating server socket");
                exit(1);
        }

        local.sun_family = AF_UNIX;
        strcpy(local.sun_path, SOCK_PATH);
        unlink(local.sun_path);
        len = strlen(local.sun_path) + sizeof(local.sun_family);
        if(bind(server_sockfd, (struct sockaddr *)&local, len) == -1)
        {
                perror("binding");
                exit(1);
        }
        if(listen(server_sockfd, 5) == -1)
        {
                perror("listen");
                exit(1);
        }

        printf("Listening...\n");
        fflush(stdout);
        if((client_sockfd = accept(server_sockfd, (struct sockaddr *)&remote, &t)) == -1)
        {
                perror("accept");
                exit(1);
        }
        int i;
        for(i=0; i < SIZE_DATA; i++){
                buff[0] = '0'+(i%15);
                send(client_sockfd, &buff, 1, 0);
        }

client:

serv_addr.sun_family = AF_UNIX;
strcpy(serv_addr.sun_path, SOCK_PATH);

if((server_sockfd = socket(AF_UNIX, SOCK_STREAM, 0)) == -1)
{
        perror("Error creating server socket");
        exit(1);
}

if ((connect(server_sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr.sun_family) + strlen(serv_addr.sun_path))) < 0) {
    perror("client connect");
    return 1;
}
while(recv(server_sockfd, &buff, 1, 0) > 0){
            //printf("data : %s\n", buff);
            send(server_sockfd, &buff, len, 0);
}