Linux: Fix Ethernet client and server (#836)

- Fix documentation.
- Add function close() to client class.
- Function connected() now return true if the connection is in
  stablished state or there is still unread data.
- Update hasClient() to check if any client has disconnected.
- Fix _accept() to better handle the case of maximum clients reached.
- Fix peek() to return the next byte of the read queue.
- Simplifies write() of the server class.
- Implements flush().
- Updates read() to non-blocking type, the same way as in Arduino.

drivers/Linux/EthernetClient.cpp

@@ -19,9 +19,11 @@
  * Based on Arduino ethernet library, Copyright (c) 2010 Arduino LLC. All right reserved.
  */
 
+#include "EthernetClient.h"
 #include <cstdio>
 #include <sys/socket.h>
 #include <sys/ioctl.h>
+#include <linux/sockios.h>
 #include <netdb.h>
 #include <arpa/inet.h>
 #include <cstring>
@@ -30,7 +32,6 @@
 #include <netinet/tcp.h>
 #include <errno.h>
 #include "log.h"
-#include "EthernetClient.h"
 
 EthernetClient::EthernetClient() : _sock(-1)
 {
@@ -67,7 +68,7 @@ int EthernetClient::connect(const char* host, uint16_t port)
 		}
 
 		if (::connect(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
-			close(sockfd);
+			::close(sockfd);
 			logError("connect: %s\n", strerror(errno));
 			continue;
 		}
@@ -113,8 +114,7 @@ size_t EthernetClient::write(const uint8_t *buf, size_t size)
 		int rc = send(_sock, buf + bytes, size, MSG_NOSIGNAL | MSG_DONTWAIT);
 		if (rc == -1) {
 			logError("send: %s\n", strerror(errno));
-			close(_sock);
+			close();
-			_sock = -1;
 			break;
 		}
 		bytes += rc;
@@ -141,16 +141,16 @@ int EthernetClient::available()
 	int count = 0;
 
 	if (_sock != -1) {
-		ioctl(_sock, FIONREAD, &count);
+		ioctl(_sock, SIOCINQ, &count);
-		return count;
 	}
-	return 0;
+
+	return count;
 }
 
 int EthernetClient::read()
 {
 	uint8_t b;
-	if ( recv(_sock, &b, 1, 0) > 0 ) {
+	if ( recv(_sock, &b, 1, MSG_DONTWAIT) > 0 ) {
 		// recv worked
 		return b;
 	} else {
@@ -159,22 +159,35 @@ int EthernetClient::read()
 	}
 }
 
-int EthernetClient::read(uint8_t *buf, size_t size)
+int EthernetClient::read(uint8_t *buf, size_t bytes)
 {
-	return recv(_sock, buf, size, 0);
+	return recv(_sock, buf, bytes, MSG_DONTWAIT);
 }
 
 int EthernetClient::peek()
 {
 	uint8_t b;
 
-	return recv(_sock, &b, 1, MSG_PEEK | MSG_DONTWAIT);
+	if (recv(_sock, &b, 1, MSG_PEEK | MSG_DONTWAIT) > 0) {
+		return b;
+	} else {
+		return -1;
+	}
 }
 
 void EthernetClient::flush()
 {
-	// There isn't much we can do here
+	int count = 0;
+
+	if (_sock != -1) {
+		while (true) {
+			ioctl(_sock, SIOCOUTQ, &count);
+			if (count == 0) {
 				return;
+			}
+			usleep(1000);
+		}
+	}
 }
 
 void EthernetClient::stop()
@@ -203,7 +216,7 @@ void EthernetClient::stop()
 
 	// if it hasn't closed, close it forcefully
 	if (s != ETHERNETCLIENT_W5100_CLOSED) {
-		close(_sock);
+		::close(_sock);
 	}
 	_sock = -1;
 }
@@ -249,17 +262,15 @@ uint8_t EthernetClient::status()
 
 uint8_t EthernetClient::connected()
 {
-	if (_sock == -1) {
+	return status() == ETHERNETCLIENT_W5100_ESTABLISHED || available();
-		return 0;
+}
-	}
 
-	if (peek() < 0) {
+void EthernetClient::close()
-		if (errno == EAGAIN) {
+{
-			return 1;
+	if (_sock != -1) {
+		::close(_sock);
+		_sock = -1;
 	}
-		return 0;
-	}
-	return 1;
 }
 
 int EthernetClient::getSocketNumber()

drivers/Linux/EthernetClient.h

@@ -57,7 +57,7 @@ public:
 	/**
 	 * @brief Initiate a connection with host:port.
 	 *
-	 * @param host host name to resolve or a stringified dotted IP address.
+	 * @param host name to resolve or a stringified dotted IP address.
 	 * @param port to connect to.
 	 * @return 1 if SUCCESS or -1 if FAILURE.
 	 */
@@ -101,7 +101,7 @@ public:
 	 */
 	size_t write(const char *buffer, size_t size);
 	/**
-	 * @brief Checks if new data is available.
+	 * @brief Returns the number of bytes available for reading.
 	 *
 	 * @return number of bytes available.
 	 */
@@ -109,27 +109,25 @@ public:
 	/**
 	 * @brief Read a byte.
 	 *
-	 * @return 0 if FAILURE or 1 if SUCCESS.
+	 * @return -1 if no data, else the first byte available.
-	 * @note This function will block (until data becomes available or timeout is reached).
 	 */
 	virtual int read();
 	/**
 	 * @brief Read a number of bytes and store in a buffer.
 	 *
-	 * @return -1 if FAILURE or number of read bytes.
+	 * @param buf buffer to write to.
-	 * @note This function will block (until data becomes available or timeout is reached).
+	 * @param bytes number of bytes to read.
+	 * @return -1 if no data or number of read bytes.
 	 */
-	virtual int read(uint8_t *buf, size_t size);
+	virtual int read(uint8_t *buf, size_t bytes);
 	/**
-	 * @brief Check if new data are available.
+	 * @brief Returns the next byte of the read queue without removing it from the queue.
 	 *
-	 * @return 0 if no data, else number of bytes available.
+	 * @return -1 if no data, else the first byte of incoming data available.
 	 */
 	virtual int peek();
 	/**
-	 * @brief Flushes the network buffers.
+	 * @brief Waits until all outgoing bytes in buffer have been sent.
-	 *
-	 * Empty function due to the way TCP works.
 	 */
 	virtual void flush();
 	/**
@@ -145,11 +143,18 @@ public:
 	 */
 	uint8_t status();
 	/**
-	 * @brief Checks whether the socket is alive.
+	 * @brief Whether or not the client is connected.
 	 *
-	 * @return 0 if disconnected or 1 if connected.
+	 * Note that a client is considered connected if the connection has been closed but
+	 * there is still unread data.
+	 *
+	 * @return 1 if the client is connected, 0 if not.
 	 */
 	virtual uint8_t connected();
+	/**
+	 * @brief Close the connection.
+	 */
+	void close();
 	/**
 	 * @brief Get the internal socket file descriptor.
 	 *

drivers/Linux/EthernetServer.cpp

@@ -19,6 +19,7 @@
  * Based on Arduino ethernet library, Copyright (c) 2010 Arduino LLC. All right reserved.
  */
 
+#include "EthernetServer.h"
 #include <cstdio>
 #include <sys/socket.h>
 #include <cstring>
@@ -30,7 +31,6 @@
 #include <fcntl.h>
 #include "log.h"
 #include "EthernetClient.h"
-#include "EthernetServer.h"
 
 EthernetServer::EthernetServer(uint16_t port, uint16_t max_clients) : port(port),
 	max_clients(max_clients), sockfd(-1)
@@ -108,6 +108,24 @@ void EthernetServer::begin(IPAddress address)
 
 bool EthernetServer::hasClient()
 {
+	// Check if any client has disconnected
+	for (size_t i = 0; i < clients.size(); ++i) {
+		EthernetClient client(clients[i]);
+		if (!client.connected()) {
+			// Checks if this disconnected client is also on the new clients list
+			for (std::list<int>::iterator it = new_clients.begin(); it != new_clients.end(); ++it) {
+				if (*it == clients[i]) {
+					new_clients.erase(it);
+					break;
+				}
+			}
+			client.stop();
+			clients[i] = clients.back();
+			clients.pop_back();
+			logDebug("Ethernet client disconnected.\n");
+		}
+	}
+
 	_accept();
 
 	return !new_clients.empty();
@@ -136,14 +154,9 @@ size_t EthernetServer::write(const uint8_t *buffer, size_t size)
 
 	while (i < clients.size()) {
 		EthernetClient client(clients[i]);
-		if (client.connected()) {
+		if (client.status() == ETHERNETCLIENT_W5100_ESTABLISHED) {
 			n += client.write(buffer, size);
 			i++;
-		} else if (!client.available()) {
-			client.stop();
-			clients[i] = clients.back();
-			clients.pop_back();
-			logDebug("Client disconnected.\n");
 		}
 	}
 
@@ -170,36 +183,6 @@ void EthernetServer::_accept()
 	struct sockaddr_storage client_addr;
 	char ipstr[INET_ADDRSTRLEN];
 
-	if (new_clients.size() + clients.size() == max_clients) {
-		// no free slots, search for a dead client
-		bool no_free_slots = true;
-		for (size_t i = 0; i < clients.size();) {
-			EthernetClient client(clients[i]);
-			if (client.connected() || client.available()) {
-				i++;
-			} else {
-				clients[i] = clients.back();
-				clients.pop_back();
-				no_free_slots = false;
-				break;
-			}
-		}
-		if (no_free_slots) {
-			for (std::list<int>::iterator it = new_clients.begin(); it != new_clients.end(); ++it) {
-				EthernetClient client(*it);
-				if (!client.connected() && !client.available()) {
-					new_clients.erase(it);
-					no_free_slots = false;
-					break;
-				}
-			}
-		}
-		if (no_free_slots) {
-			logDebug("Max number of ethernet clients reached.\n");
-			return;
-		}
-	}
-
 	sin_size = sizeof client_addr;
 	new_fd = accept(sockfd, (struct sockaddr *)&client_addr, &sin_size);
 	if (new_fd == -1) {
@@ -209,6 +192,13 @@ void EthernetServer::_accept()
 		return;
 	}
 
+	if (clients.size() == max_clients) {
+		// no free slots, search for a dead client
+		close(new_fd);
+		logDebug("Max number of ethernet clients reached.\n");
+		return;
+	}
+
 	new_clients.push_back(new_fd);
 	clients.push_back(new_fd);
 

drivers/Linux/EthernetServer.h

@@ -70,7 +70,7 @@ public:
 	/**
 	 * @brief Get the new connected client.
 	 *
-	 * @return client class object if a new client has connected else -1.
+	 * @return a EthernetClient object; if no new client has connected, this object will evaluate to false.
 	 */
 	EthernetClient available();
 	/**
@@ -106,8 +106,8 @@ public:
 
 private:
 	uint16_t port; //!< @brief Port number for the network socket.
-	std::list<int> new_clients; //!< Socket list of new clients.
+	std::list<int> new_clients; //!< Socket list of new connected clients.
-	std::vector<int> clients; //!< @brief Socket list of clients.
+	std::vector<int> clients; //!< @brief Socket list of connected clients.
 	uint16_t max_clients; //!< @brief The maximum number of allowed clients.
 	int sockfd; //!< @brief Network socket used to accept connections.