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;
@@ -151,24 +156,56 @@ IsmasClient::sendRequestReceiveResponse(int port, QString const &request) {
     int loop = 0;
     int bytesWritten = 0;
     while (bytesWritten < bytesToWrite) {
-        int n = ::sendto(sockfd, buf+bytesWritten, bytesToWrite-bytesWritten, 0, NULL, 0);
+        errno = 0;
-        if (n >= 0) {
+        FD_ZERO(&wset);
-            bytesWritten += n;
+        FD_SET(sockfd, &wset);
-        } else {
+        maxfdp1 = sockfd + 1;
-            if (errno == EWOULDBLOCK) {
+        tv.tv_sec = 60;  /* 60 secs timeout for read and write -> APISM cuts the connection after 30s */
-                if (++loop < 10) {
+        tv.tv_usec = 0;
-                    QThread::msleep(500);
+
-                    continue;
+        int const w = select(maxfdp1, NULL, &wset, NULL, &tv);
-                }
+        if (w < 0) { // error
-                printErrorMessage(port, clientIP, clientPort,
-                    QString("WRITE TIMEOUT %1(").arg(loop) + strerror(errno) + ")");
-                ::close(sockfd);
-                return std::nullopt;
-            } else
             if (errno == EINTR) {
                 printErrorMessage(port, clientIP, clientPort,
-                    QString("WRITE INTERRUPTED BY SIGNAL (1) (") + strerror(errno) + ")");
+                    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;
+            } else {
+                if (errno == EWOULDBLOCK) {
+                    if (++loop < 10) {
+                        QThread::msleep(500);
+                        continue;
+                    }
+                    printErrorMessage(port, clientIP, clientPort,
+                        QString("WRITE TIMEOUT %1(").arg(loop) + strerror(errno) + ")");
+                    ::close(sockfd);
+                    return std::nullopt;
+                } else
+                if (errno == EINTR) {
+                    printErrorMessage(port, clientIP, clientPort,
+                        QString("WRITE INTERRUPTED BY SIGNAL (1) (") + strerror(errno) + ")");
+                    continue;
+                }
             }
         }
     }
@@ -188,33 +225,66 @@ IsmasClient::sendRequestReceiveResponse(int port, QString const &request) {
     int bytesRead = 0;
     while (bytesRead < bytesToRead) {
         errno = 0;
-        int n = ::recvfrom(sockfd, buf+bytesRead, bytesToRead-bytesRead,
+        FD_ZERO(&rset);
-                           0, NULL, NULL);
+        FD_SET(sockfd, &rset);
-        if (n > 0) { //
+        maxfdp1 = sockfd + 1;
-            bytesRead += n;
+        tv.tv_sec = 60;  /* 60 secs timeout for read and write */
-        } else
+        tv.tv_usec = 0;
-        if (n == 0) {
+
-            // The return value will be 0 when the peer has performed an orderly shutdown.
+        int const r = select(maxfdp1, &rset, NULL, NULL, &tv);
-            printErrorMessage(port, clientIP, clientPort,
+        if (r < 0) { // error
-                QString("PEER CLOSED CONNECTION (") + strerror(errno) + ")");
-            ::close(sockfd);
-            return std::nullopt;
-        } else
-        if (n < 0) {
-            if (errno == EWOULDBLOCK) {
-                if (++loop < 10) {
-                    QThread::msleep(500);
-                    continue;
-                }
-                printErrorMessage(port, clientIP, clientPort,
-                        QString("READ TIMEOUT %1(").arg(loop) + strerror(errno) + ")");
-                ::close(sockfd);
-                return std::nullopt;
-            }
             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) { //
+                    bytesRead += n;
+                } else
+                if (n == 0) {
+                    // The return value will be 0 when the peer has performed an orderly shutdown.
+                    printErrorMessage(port, clientIP, clientPort,
+                        QString("PEER CLOSED CONNECTION (") + strerror(errno) + ")");
+                    ::close(sockfd);
+                    return std::nullopt;
+                } else
+                if (n < 0) {
+                    if (errno == EWOULDBLOCK) { // check just in case
+                        if (++loop < 10) {
+                            QThread::msleep(500);
+                            continue;
+                        }
+                        printErrorMessage(port, clientIP, clientPort,
+                                QString("READ TIMEOUT %1(").arg(loop) + strerror(errno) + ")");
+                        ::close(sockfd);
+                        return std::nullopt;
+                    }
+                    if (errno == EINTR) {
+                        printErrorMessage(port, clientIP, clientPort,
+                            QString("INTERRUPTED BY SIGNAL (2) (") + strerror(errno) + ")");
+                        continue;
+                    }
+                }
             }
         }