SO_SNDTIMEO and SO_RCVTIMEO socket options have turned out not to be reliable.

Use select() for detecting timeout on socket (read and write).

ismas/ismas_client.cpp

@@ -137,7 +137,12 @@ IsmasClient::sendRequestReceiveResponse(int port, QString const &request) {
     so_linger.l_onoff = 1;
     so_linger.l_linger = 0;
 
+    int maxfdp1;
+    fd_set rset;
+    fd_set wset;
+
     setsockopt(sockfd, SOL_SOCKET, SO_LINGER, &so_linger, sizeof(so_linger));
+    // no reliable, but does not harm, as we use select() as well
     setsockopt(sockfd, SOL_SOCKET, SO_SNDTIMEO, &tv, sizeof(tv));
     setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv));
     int flag = 1;
@@ -151,6 +156,37 @@ IsmasClient::sendRequestReceiveResponse(int port, QString const &request) {
     int loop = 0;
     int bytesWritten = 0;
     while (bytesWritten < bytesToWrite) {
+        errno = 0;
+        FD_ZERO(&wset);
+        FD_SET(sockfd, &wset);
+        maxfdp1 = sockfd + 1;
+        tv.tv_sec = 60;  /* 60 secs timeout for read and write -> APISM cuts the connection after 30s */
+        tv.tv_usec = 0;
+
+        int const w = select(maxfdp1, NULL, &wset, NULL, &tv);
+        if (w < 0) { // error
+            if (errno == EINTR) {
+                printErrorMessage(port, clientIP, clientPort,
+                    QString("INTERRUPTED BY SIGNAL (1) (") + strerror(errno) + ")");
+                continue;
+            } else {
+                printErrorMessage(port, clientIP, clientPort,
+                        QString("SELECT-ERROR (WRITE) %1(").arg(loop) + strerror(errno) + ")");
+                ::close(sockfd);
+                return std::nullopt;
+            }
+        } else
+        if (w == 0) { // timeout
+            printErrorMessage(port, clientIP, clientPort,
+                    QString("SELECT-TIMEOUT (WRITE) %1(").arg(loop) + strerror(errno) + ")");
+            if (++loop < 10) {
+                QThread::msleep(500);
+                continue;
+            }
+            ::close(sockfd);
+            return std::nullopt;
+        } else
+        if (w > 0) {
             int n = ::sendto(sockfd, buf+bytesWritten, bytesToWrite-bytesWritten, 0, NULL, 0);
             if (n >= 0) {
                 bytesWritten += n;
@@ -172,6 +208,7 @@ IsmasClient::sendRequestReceiveResponse(int port, QString const &request) {
                 }
             }
         }
+    }
 
     // DO NOT USE SHUTDOWN! APISM CAN NOT COPE WITH IT
     // errno = 0;
@@ -188,6 +225,37 @@ IsmasClient::sendRequestReceiveResponse(int port, QString const &request) {
     int bytesRead = 0;
     while (bytesRead < bytesToRead) {
         errno = 0;
+        FD_ZERO(&rset);
+        FD_SET(sockfd, &rset);
+        maxfdp1 = sockfd + 1;
+        tv.tv_sec = 60;  /* 60 secs timeout for read and write */
+        tv.tv_usec = 0;
+
+        int const r = select(maxfdp1, &rset, NULL, NULL, &tv);
+        if (r < 0) { // error
+            if (errno == EINTR) {
+                printErrorMessage(port, clientIP, clientPort,
+                    QString("INTERRUPTED BY SIGNAL (2) (") + strerror(errno) + ")");
+                continue;
+            } else {
+                printErrorMessage(port, clientIP, clientPort,
+                        QString("SELECT-ERROR (READ) %1(").arg(loop) + strerror(errno) + ")");
+                ::close(sockfd);
+                return std::nullopt;
+            }
+        } else
+        if (r == 0) { // timeout
+            printErrorMessage(port, clientIP, clientPort,
+                    QString("SELECT-TIMEOUT (READ) %1(").arg(loop) + strerror(errno) + ")");
+            if (++loop < 10) {
+                QThread::msleep(500);
+                continue;
+            }
+            ::close(sockfd);
+            return std::nullopt;
+        } else
+        if (r > 0) {
+            if (FD_ISSET(sockfd, &rset)) {
                 int n = ::recvfrom(sockfd, buf+bytesRead, bytesToRead-bytesRead,
                                    0, NULL, NULL);
                 if (n > 0) { //
@@ -201,7 +269,7 @@ IsmasClient::sendRequestReceiveResponse(int port, QString const &request) {
                     return std::nullopt;
                 } else
                 if (n < 0) {
-            if (errno == EWOULDBLOCK) {
+                    if (errno == EWOULDBLOCK) { // check just in case
                         if (++loop < 10) {
                             QThread::msleep(500);
                             continue;
@@ -217,6 +285,8 @@ IsmasClient::sendRequestReceiveResponse(int port, QString const &request) {
                         continue;
                     }
                 }
+            }
+        }
 
         printInfoMessage(port, clientIP, clientPort, QString("MESSAGE RECEIVED ") + buf);
         QString response(buf);