coap-chat: a simple chat application using gCoAP

coap-chat/Makefile

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+# name of your application
+APPLICATION = coap_chat
+
+# If no BOARD is found in the environment, use this default:
+BOARD ?= native
+
+# This has to be the absolute path to the RIOT base directory:
+RIOTBASE ?= $(CURDIR)/../../RIOT
+
+USEMODULE += gnrc_netdev_default
+USEMODULE += auto_init_gnrc_netif
+# Specify the mandatory networking modules
+USEMODULE += gnrc_ipv6_default
+USEMODULE += gcoap
+# Additional networking modules that can be dropped if not needed
+USEMODULE += gnrc_icmpv6_echo
+# Add also the shell, some shell commands
+USEMODULE += shell
+USEMODULE += shell_commands
+
+# Comment this out to disable code in RIOT that does safety checking
+# which is not needed in a production environment but helps in the
+# development process:
+DEVELHELP ?= 0
+
+# Change this to 0 show compiler invocation lines by default:
+QUIET ?= 1
+
+include $(RIOTBASE)/Makefile.include

coap-chat/README.md

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+## About
+
+This application provides a simple command line chat using (g)CoAP as transport.
+It allows to send (short) messages to any (IPv6) address reachable by the node.
+All messages are sent to and received for a CoAP resource with path `/chat`.
+
+## Usage
+
+To send messages use the `chat` shell command, it can be invoked as follows:
+
+```
+chat <destination> <nickname> <message>
+```
+
+- **destination:** a reachable IPv6 address, may even be multicast `ff02::1`
+- **nickname:** your chat nickname, anything is allowed, but keep it short
+- **message:** what ever text you want to share, be brief, size is limited
+
+The message format is plain text and will be send as *nickname: message*, the
+maximum message size is 63 chars - so keep *nickname*  and *message* short :)
+Please be aware that all CoAP messages are sent as non-confirmable, hence there
+is no retransmission in case of packet loss.
+
+## Notes
+
+The code base of this application aims for simplicity, thus it only provides
+a minimalistic set of functions. An advanced CoAP application can be found in
+the [RIOT examples](https://github.com/RIOT-OS/RIOT/tree/master/examples/gcoap).
+
+The application also ships with a number of standard shell commands, such as
+`ifconfig` to allow for network interface configuration. Just type `help` in
+the shell to see a full list and description of all available commands.
+
+By default this application is configured to run as an IPv6 node, i.e. it does
+not include any routing or relaying functionality - such needs to be handled
+by other nodes.

coap-chat/coap.c

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+/*
+ * Copyright (c) 2018 HAW Hamburg
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     applications
+ * @{
+ *
+ * @file
+ * @brief       coap-chat - CoAP helper functions
+ *
+ * @author      Sebastian Meiling <[email protected]>
+ *
+ * @}
+ */
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "net/gcoap.h"
+
+#define ENABLE_DEBUG (0)
+#include "debug.h"
+
+#define COAP_CHAT_PATH      "/chat"
+
+static ssize_t _chat_handler(coap_pkt_t *pdu, uint8_t *buf, size_t len, void *ctx);
+
+/* CoAP resources */
+static const coap_resource_t _resources[] = {
+    { COAP_CHAT_PATH, COAP_POST, _chat_handler, NULL },
+};
+
+static gcoap_listener_t _listener = {
+    &_resources[0],
+    sizeof(_resources) / sizeof(_resources[0]),
+    NULL
+};
+
+static ssize_t _chat_handler(coap_pkt_t *pdu, uint8_t *buf, size_t len, void *ctx)
+{
+    (void)ctx;
+
+    if (pdu->payload_len > 0) {
+        printf("\n[ CHAT ] %.*s\n\n", pdu->payload_len, (char *)pdu->payload);
+        return gcoap_response(pdu, buf, len, COAP_CODE_CHANGED);
+    }
+    return gcoap_response(pdu, buf, len, COAP_CODE_BAD_REQUEST);
+}
+
+static size_t _send(uint8_t *buf, size_t len, char *addr_str)
+{
+    ipv6_addr_t addr;
+    sock_udp_ep_t remote;
+
+    remote.family = AF_INET6;
+
+    /* parse for interface */
+    int iface = ipv6_addr_split_iface(addr_str);
+    if (iface == -1) {
+        if (gnrc_netif_numof() == 1) {
+            /* assign the single interface found in gnrc_netif_numof() */
+            remote.netif = (uint16_t)gnrc_netif_iter(NULL)->pid;
+        }
+        else {
+            remote.netif = SOCK_ADDR_ANY_NETIF;
+        }
+    }
+    else {
+        if (gnrc_netif_get_by_pid(iface) == NULL) {
+            DEBUG("[CoAP] interface not valid");
+            return 0;
+        }
+        remote.netif = iface;
+    }
+
+    /* parse destination address */
+    if (ipv6_addr_from_str(&addr, addr_str) == NULL) {
+        DEBUG("[CoAP] unable to parse destination address");
+        return 0;
+    }
+    if ((remote.netif == SOCK_ADDR_ANY_NETIF) && ipv6_addr_is_link_local(&addr)) {
+        DEBUG("[CoAP] must specify interface for link local target");
+        return 0;
+    }
+    memcpy(&remote.addr.ipv6[0], &addr.u8[0], sizeof(addr.u8));
+
+    /* parse port */
+    remote.port = GCOAP_PORT;
+
+    return gcoap_req_send2(buf, len, &remote, NULL);
+}
+
+int coap_post(char *addr, char *msgbuf, size_t msglen)
+{
+    assert(msglen < GCOAP_PDU_BUF_SIZE);
+
+    coap_pkt_t pdu;
+    uint8_t buf[GCOAP_PDU_BUF_SIZE];
+    size_t len = 0;
+
+    gcoap_req_init(&pdu, buf, GCOAP_PDU_BUF_SIZE, COAP_POST, COAP_CHAT_PATH);
+
+    memcpy(pdu.payload, msgbuf, msglen);
+
+    len = gcoap_finish(&pdu, msglen, COAP_FORMAT_TEXT);
+
+    DEBUG("[CoAP] coap_post: sending msg ID %u, %u bytes\n",
+          coap_get_id(&pdu), (unsigned) len);
+
+    if (!_send(buf, len, addr)) {
+        puts("[CoAP] coap_post: msg send failed");
+        return -1;
+    }
+    return len;
+}
+
+void coap_init(void)
+{
+    gcoap_register_listener(&_listener);
+}

coap-chat/main.c

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+/*
+ * Copyright (c) 2018 HAW Hamburg
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     applications
+ * @{
+ *
+ * @file
+ * @brief       coap-chat - Main loop and shell handlers
+ *
+ * @author      Sebastian Meiling <[email protected]>
+ *
+ * @}
+ */
+
+#include <stdio.h>
+#include "msg.h"
+
+#include "net/gcoap.h"
+#include "kernel_types.h"
+#include "shell.h"
+
+#define BUFLEN          (64U)
+#define MAIN_QUEUE_SIZE (4)
+
+static msg_t _main_msg_queue[MAIN_QUEUE_SIZE];
+
+extern int coap_post(const char *addr, const char *buf, size_t buflen);
+extern void coap_init(void);
+
+int chat(int argc, char **argv)
+{
+    if (argc < 4) {
+        puts("usage: chat <addr> <nick> <msg>");
+        return 1;
+    }
+
+    char buf[BUFLEN] = { 0 };
+    size_t len = snprintf(buf, BUFLEN, "%s: %s", argv[2], argv[3]);
+    for (int i = 4; i < argc; ++i) {
+        len += snprintf(buf + len, BUFLEN - len, " %s", argv[i]);
+    }
+    coap_post(argv[1], buf, len);
+
+    return 0;
+}
+
+static const shell_command_t shell_commands[] = {
+    { "chat", "CoAP chat", chat },
+    { NULL, NULL, NULL }
+};
+
+int main(void)
+{
+    /* for the thread running the shell */
+    msg_init_queue(_main_msg_queue, MAIN_QUEUE_SIZE);
+    /* init coap listener */
+    coap_init();
+    /* start shell */
+    puts("All up, running the shell now");
+    char line_buf[SHELL_DEFAULT_BUFSIZE];
+    shell_run(shell_commands, line_buf, SHELL_DEFAULT_BUFSIZE);
+
+    /* should never be reached */
+    return 0;
+}