samples: net: Add socket-based echo server example

The example source code is POSIX-compatible (modulo include files),
i.e. can be built and behaves the same way for Zephyr and a POSIX
system (e.g. Linux). Makefile.posix is available for the latter.

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

samples/net/socket_echo/Makefile

@@ -0,0 +1,18 @@
+# Makefile - simple 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/socket_echo/Makefile.posix

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

samples/net/socket_echo/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/socket_echo/src/Makefile

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

samples/net/socket_echo/src/socket_echo.c

@@ -0,0 +1,76 @@
+/*
+ * 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>
+
+#define init_net()
+
+#else
+
+#include <net/socket.h>
+#include <kernel.h>
+#include <net_sample_app.h>
+
+void init_net(void)
+{
+	int ret = net_sample_app_init("socket_echo", NET_SAMPLE_NEED_IPV4,
+				      K_SECONDS(3));
+
+	if (ret < 0) {
+		printf("Application init failed\n");
+		k_panic();
+	}
+}
+
+#endif
+
+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));
+
+	listen(serv, 5);
+
+	while (1) {
+		struct sockaddr_in client_addr;
+		socklen_t client_addr_len = sizeof(client_addr);
+		char addr_str[32];
+		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\n", addr_str);
+
+		while (1) {
+			char buf[128];
+			int len = recv(client, buf, sizeof(buf), 0);
+
+			if (len == 0) {
+				break;
+			}
+			send(client, buf, len, 0);
+		}
+
+		close(client);
+		printf("Connection from %s closed\n", addr_str);
+	}
+}