1 files changed, 188 insertions, 0 deletions
diff --git a/src/UDPServer/UDPServer.cpp b/src/UDPServer/UDPServer.cpp
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+/*
+ * http://linux.m2osw.com/c-implementation-udp-clientserver
+ *
+ * UDPServer.cpp
+ *
+ *  Created on: 29.06.2016
+ *      Author: Tobias Frust
+ */
+
+// ========================= SEVER =========================
+
+/** \brief Initialize a UDP server object.
+ *
+ * This function initializes a UDP server object making it ready to
+ * receive messages.
+ *
+ * The server address and port are specified in the constructor so
+ * if you need to receive messages from several different addresses
+ * and/or port, you'll have to create a server for each.
+ *
+ * The address is a string and it can represent an IPv4 or IPv6
+ * address.
+ *
+ * Note that this function calls connect() to connect the socket
+ * to the specified address. To accept data on different UDP addresses
+ * and ports, multiple UDP servers must be created.
+ *
+ * \note
+ * The socket is open in this process. If you fork() or exec() then the
+ * socket will be closed by the operating system.
+ *
+ * \warning
+ * We only make use of the first address found by getaddrinfo(). All
+ * the other addresses are ignored.
+ *
+ * \exception udp_client_server_runtime_error
+ * The udp_client_server_runtime_error exception is raised when the address
+ * and port combinaison cannot be resolved or if the socket cannot be
+ * opened.
+ *
+ * \param[in] addr  The address we receive on.
+ * \param[in] port  The port we receive from.
+ */
+UDPServer::UDPServer(const std::string& addr, int port)
+    : f_port(port)
+    , f_addr(addr)
+{
+    char decimal_port[16];
+    snprintf(decimal_port, sizeof(decimal_port), "%d", f_port);
+    decimal_port[sizeof(decimal_port) / sizeof(decimal_port[0]) - 1] = '\0';
+    struct addrinfo hints;
+    memset(&hints, 0, sizeof(hints));
+    hints.ai_family = AF_UNSPEC;
+    hints.ai_socktype = SOCK_DGRAM;
+    hints.ai_protocol = IPPROTO_UDP;
+    int r(getaddrinfo(addr.c_str(), decimal_port, &hints, &f_addrinfo));
+    if(r != 0 || f_addrinfo == NULL)
+    {
+        throw udp_client_server_runtime_error(("invalid address or port for UDP socket: \"" + addr + ":" + decimal_port + "\"").c_str());
+    }
+    f_socket = socket(f_addrinfo->ai_family, SOCK_DGRAM | SOCK_CLOEXEC, IPPROTO_UDP);
+    if(f_socket == -1)
+    {
+        freeaddrinfo(f_addrinfo);
+        throw udp_client_server_runtime_error(("could not create UDP socket for: \"" + addr + ":" + decimal_port + "\"").c_str());
+    }
+    r = bind(f_socket, f_addrinfo->ai_addr, f_addrinfo->ai_addrlen);
+    if(r != 0)
+    {
+        freeaddrinfo(f_addrinfo);
+        close(f_socket);
+        throw udp_client_server_runtime_error(("could not bind UDP socket with: \"" + addr + ":" + decimal_port + "\"").c_str());
+    }
+}
+
+/** \brief Clean up the UDP server.
+ *
+ * This function frees the address info structures and close the socket.
+ */
+UDPServer::~UDPServer()
+{
+    freeaddrinfo(f_addrinfo);
+    close(f_socket);
+}
+
+/** \brief The socket used by this UDP server.
+ *
+ * This function returns the socket identifier. It can be useful if you are
+ * doing a select() on many sockets.
+ *
+ * \return The socket of this UDP server.
+ */
+int UDPServer::get_socket() const
+{
+    return f_socket;
+}
+
+/** \brief The port used by this UDP server.
+ *
+ * This function returns the port attached to the UDP server. It is a copy
+ * of the port specified in the constructor.
+ *
+ * \return The port of the UDP server.
+ */
+int UDPServer::get_port() const
+{
+    return f_port;
+}
+
+/** \brief Return the address of this UDP server.
+ *
+ * This function returns a verbatim copy of the address as passed to the
+ * constructor of the UDP server (i.e. it does not return the canonalized
+ * version of the address.)
+ *
+ * \return The address as passed to the constructor.
+ */
+std::string UDPServer::get_addr() const
+{
+    return f_addr;
+}
+
+/** \brief Wait on a message.
+ *
+ * This function waits until a message is received on this UDP server.
+ * There are no means to return from this function except by receiving
+ * a message. Remember that UDP does not have a connect state so whether
+ * another process quits does not change the status of this UDP server
+ * and thus it continues to wait forever.
+ *
+ * Note that you may change the type of socket by making it non-blocking
+ * (use the get_socket() to retrieve the socket identifier) in which
+ * case this function will not block if no message is available. Instead
+ * it returns immediately.
+ *
+ * \param[in] msg  The buffer where the message is saved.
+ * \param[in] max_size  The maximum size the message (i.e. size of the \p msg buffer.)
+ *
+ * \return The number of bytes read or -1 if an error occurs.
+ */
+int UDPServer::recv(char *msg, size_t max_size)
+{
+    return ::recv(f_socket, msg, max_size, 0);
+}
+
+/** \brief Wait for data to come in.
+ *
+ * This function waits for a given amount of time for data to come in. If
+ * no data comes in after max_wait_ms, the function returns with -1 and
+ * errno set to EAGAIN.
+ *
+ * The socket is expected to be a blocking socket (the default,) although
+ * it is possible to setup the socket as non-blocking if necessary for
+ * some other reason.
+ *
+ * This function blocks for a maximum amount of time as defined by
+ * max_wait_ms. It may return sooner with an error or a message.
+ *
+ * \param[in] msg  The buffer where the message will be saved.
+ * \param[in] max_size  The size of the \p msg buffer in bytes.
+ * \param[in] max_wait_ms  The maximum number of milliseconds to wait for a message.
+ *
+ * \return -1 if an error occurs or the function timed out, the number of bytes received otherwise.
+ */
+int UDPServer::timed_recv(char *msg, size_t max_size, int max_wait_ms)
+{
+    fd_set s;
+    FD_ZERO(&s);
+    FD_SET(f_socket, &s);
+    struct timeval timeout;
+    timeout.tv_sec = max_wait_ms / 1000;
+    timeout.tv_usec = (max_wait_ms % 1000) * 1000;
+    int retval = select(f_socket + 1, &s, &s, &s, &timeout);
+    if(retval == -1)
+    {
+        // select() set errno accordingly
+        return -1;
+    }
+    if(retval > 0)
+    {
+        // our socket has data
+        return ::recv(f_socket, msg, max_size, 0);
+    }
+
+    // our socket has no data
+    errno = EAGAIN;
+    return -1;
+}