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Fixed bug with sio3/socket interaction. #557

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Fixed bug with sio3/socket interaction. #557

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45 changes: 31 additions & 14 deletions iodevices/altair-88-sio.c
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Original file line number Diff line number Diff line change
Expand Up @@ -201,6 +201,35 @@ void altair_sio0_data_out(BYTE data)
sio0_stat |= 0b10000000;
}


/*
* Helper function to check and accept incoming socket connection.
* Called from both sio3_status_in() and sio3_data_in() to ensure
* the connection is established regardless of which port is accessed
* first. Fixes a bug where reading data port 7 directly (without
* polling status port 6 first) would always return stale data because
* accept() was only called from the status path.
*/
static void sio3_check_connection(void)
{
struct pollfd p[1];
if (ucons[0].ssc == 0) {
p[0].fd = ucons[0].ss;
p[0].events = POLLIN;
p[0].revents = 0;
poll(p, 1, 0);
if (p[0].revents) {
if ((ucons[0].ssc = accept(ucons[0].ss, NULL, NULL)) == -1) {
LOGW(TAG, "can't accept server socket");
ucons[0].ssc = 0;
}
}
}
}




/*
* read status register
*
Expand All @@ -214,20 +243,7 @@ BYTE altair_sio3_status_in(void)
struct pollfd p[1];

/* if socket not connected check for a new connection */
if (ucons[0].ssc == 0) {
p[0].fd = ucons[0].ss;
p[0].events = POLLIN;
p[0].revents = 0;
poll(p, 1, 0);
/* accept a new connection */
if (p[0].revents) {
if ((ucons[0].ssc = accept(ucons[0].ss, NULL,
NULL)) == -1) {
LOGW(TAG, "can't accept server socket");
ucons[0].ssc = 0;
}
}
}
sio3_check_connection();

sio3_t2 = get_clock_us();
if (sio3_baud_rate > 0 &&
Expand Down Expand Up @@ -268,6 +284,7 @@ BYTE altair_sio3_data_in(void)
static BYTE last;
struct pollfd p[1];

sio3_check_connection();
/* if not connected return last */
if (ucons[0].ssc == 0)
return last;
Expand Down