samples: sockets: Add async echo server example

Implements asynchronous TCP echo server using non-blocking sockets
and poll, with concurrent connections support.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>

samples/net/sockets/echo_async/Makefile

@@ -0,0 +1,18 @@
+# Makefile - asynchronous socket-based echo server
+
+#
+# Copyright (c) 2017 Linaro Limited
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+BOARD ?= qemu_x86
+CONF_FILE ?= prj_$(BOARD).conf
+
+include $(ZEPHYR_BASE)/Makefile.inc
+
+ifeq ($(CONFIG_NET_L2_BLUETOOTH), y)
+	QEMU_EXTRA_FLAGS = -serial unix:/tmp/bt-server-bredr
+else
+	include $(ZEPHYR_BASE)/samples/net/common/Makefile.ipstack
+endif

samples/net/sockets/echo_async/Makefile.posix

@@ -0,0 +1,4 @@
+# This makefile builds sample for POSIX system, like Linux
+
+socket_echo: src/socket_echo.c
+	$(CC) $^ -o $@

samples/net/sockets/echo_async/prj_qemu_x86.conf

@@ -0,0 +1,26 @@
+# General config
+CONFIG_NEWLIB_LIBC=y
+
+# Networking config
+CONFIG_NETWORKING=y
+CONFIG_NET_IPV4=y
+CONFIG_NET_IPV6=n
+CONFIG_NET_TCP=y
+CONFIG_NET_SOCKETS=y
+CONFIG_NET_SOCKETS_POSIX_NAMES=y
+
+# Network driver config
+CONFIG_NET_SLIP_TAP=y
+CONFIG_TEST_RANDOM_GENERATOR=y
+
+# Without CONFIG_NET_BUF_LOG printf() doesn't work
+CONFIG_NET_BUF_LOG=y
+
+# Network address config
+CONFIG_NET_APP_SETTINGS=y
+CONFIG_NET_APP_MY_IPV4_ADDR="192.0.2.1"
+CONFIG_NET_APP_PEER_IPV4_ADDR="192.0.2.2"
+
+# Network debug config
+#CONFIG_NET_DEBUG_SOCKETS=y
+CONFIG_SYS_LOG_NET_LEVEL=2

samples/net/sockets/echo_async/sample.yaml

@@ -0,0 +1,8 @@
+sample:
+    description: BSD Sockets API TCP echo server sample using non-blocking sockets
+    name: socket_echo_async
+tests:
+-   test:
+        build_only: true
+        platform_whitelist: qemu_x86
+        tags: net

samples/net/sockets/echo_async/src/Makefile

@@ -0,0 +1,3 @@
+include $(ZEPHYR_BASE)/samples/net/common/Makefile.common
+
+obj-y += socket_echo.o

samples/net/sockets/echo_async/src/socket_echo.c

@@ -0,0 +1,140 @@
+/*
+ * Copyright (c) 2017 Linaro Limited
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <stdio.h>
+
+#ifndef __ZEPHYR__
+
+#include <netinet/in.h>
+#include <sys/socket.h>
+#include <arpa/inet.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <poll.h>
+
+#define init_net()
+
+#else
+
+#include <sys/fcntl.h>
+#include <net/socket.h>
+#include <kernel.h>
+#include <net/net_app.h>
+
+void init_net(void)
+{
+	int ret = net_app_init("socket_echo", NET_APP_NEED_IPV4, K_SECONDS(3));
+
+	if (ret < 0) {
+		printf("Application init failed\n");
+		k_panic();
+	}
+}
+
+#endif
+
+/* Number of simultaneous connections will be minus 1 */
+#define NUM_FDS 4
+
+struct pollfd pollfds[NUM_FDS];
+int pollnum;
+
+static void nonblock(int fd)
+{
+	int fl = fcntl(fd, F_GETFL, 0);
+	fcntl(fd, F_SETFL, fl | O_NONBLOCK);
+}
+
+int pollfds_add(int fd)
+{
+	int i;
+	if (pollnum < NUM_FDS) {
+		i = pollnum++;
+	} else {
+		for (i = 0; i < NUM_FDS; i++) {
+			if (pollfds[i].fd < 0) {
+				goto found;
+			}
+		}
+
+		return -1;
+	}
+
+found:
+	pollfds[i].fd = fd;
+	pollfds[i].events = POLLIN;
+
+	return 0;
+}
+
+void pollfds_del(int fd)
+{
+	for (int i = 0; i < pollnum; i++) {
+		if (pollfds[i].fd == fd) {
+			pollfds[i].fd = -1;
+			break;
+		}
+	}
+}
+
+int main(void)
+{
+	int serv;
+	struct sockaddr_in bind_addr;
+
+	init_net();
+
+	serv = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
+
+	bind_addr.sin_family = AF_INET;
+	bind_addr.sin_addr.s_addr = htonl(INADDR_ANY);
+	bind_addr.sin_port = htons(4242);
+	bind(serv, (struct sockaddr *)&bind_addr, sizeof(bind_addr));
+
+	nonblock(serv);
+	pollfds_add(serv);
+
+	listen(serv, 5);
+
+	while (1) {
+		struct sockaddr_in client_addr;
+		socklen_t client_addr_len = sizeof(client_addr);
+		char addr_str[32];
+
+		poll(pollfds, pollnum, -1);
+		for (int i = 0; i < pollnum; i++) {
+			if (!(pollfds[i].revents & POLLIN)) {
+				continue;
+			}
+			int fd = pollfds[i].fd;
+			if (fd == serv) {
+				int client = accept(serv, (struct sockaddr *)&client_addr,
+						    &client_addr_len);
+				inet_ntop(client_addr.sin_family, &client_addr.sin_addr,
+					  addr_str, sizeof(addr_str));
+				printf("Connection from %s fd=%d\n", addr_str, client);
+				if (pollfds_add(client) < 0) {
+					static char msg[] = "Too many connections\n";
+					send(client, msg, sizeof(msg) - 1, 0);
+					close(client);
+				} else {
+					nonblock(client);
+				}
+			} else {
+				char buf[128];
+				int len = recv(fd, buf, sizeof(buf), 0);
+				if (len == 0) {
+					pollfds_del(fd);
+					close(fd);
+					printf("Connection fd=%d closed\n", fd);
+				} else {
+					/* We assume this won't be short write, d'oh */
+					send(fd, buf, len, 0);
+				}
+			}
+		}
+	}
+}