add socket snippet

Socket_snippet/client.c

@@ -0,0 +1,120 @@
+/*
+ * This file is part of the socksnippet project.
+ * Copyright 2022 Edward V. Emelianov <edward.emelianoff@gmail.com>.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+// client-side functions
+#include <stdio.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <usefull_macros.h>
+
+#include "client.h"
+#include "socket.h"
+
+/**
+ * @brief processData - process here some actions and make messages for server
+ * @param buf (o) - buffer for answer
+ * @param l - max length of buf
+ * @return amount of answer bytes
+ */
+static int process_data(char *buf, int l){
+    if(!buf || !l) return 0;
+    /* USERCODE: get here some data to send */
+    static double t0 = 0.;
+    if(dtime() - t0 > 1.){
+        t0 = dtime();
+        // send random commands each 1 second
+        int x = rand() % 600;
+        const char *cmd = NULL;
+        if(x < 100) cmd = "time";
+        else if(x < 200) cmd = "getval1";
+        else if(x < 300) cmd = "getval2";
+        else if(x < 400) cmd = "ping";
+        if(cmd) snprintf(buf, l, "%s", cmd);
+        else{
+            if(x < 500) snprintf(buf, l, "setval1=%d", rand() & 0xff);
+            else snprintf(buf, l, "setval2=%d", rand() & 0xff);
+        }
+        return strlen(buf);
+    }
+    return 0;
+}
+
+/**
+ * @brief process_server_message - parse messages from server and make an answer
+ * @param buf (io) - incoming message (the answer will be in this buffer)
+ * @param l - buff max length
+ * @return amount of answer bytes
+ */
+static int process_server_message(char *buf, int l){
+    /* USERCODE inside this funtion */
+    if(!buf || !l) return 0;
+    // just show on screen
+    green("SERVER send: %s\n", buf);
+    return 0;
+}
+
+
+/**
+ * check data from  fd (polling function for client)
+ * @param fd - file descriptor
+ * @return 0 in case of timeout, 1 in case of fd have data, -1 if error
+ */
+static int canberead(int fd){
+    fd_set fds;
+    struct timeval timeout;
+    timeout.tv_sec = 0;
+    timeout.tv_usec = 100;
+    FD_ZERO(&fds);
+    FD_SET(fd, &fds);
+    do{
+        int rc = select(fd+1, &fds, NULL, NULL, &timeout);
+        if(rc < 0){
+            if(errno != EINTR){
+                LOGWARN("select()");
+                WARN("select()");
+                return -1;
+            }
+            continue;
+        }
+        break;
+    }while(1);
+    if(FD_ISSET(fd, &fds)){
+        //DBG("FD_ISSET");
+        return 1;
+    }
+    return 0;
+}
+
+void client(int sock){
+    char buf[BUFLEN];
+    while(1){
+        int l = process_data(buf, BUFLEN-1);
+        if(l) sendmessage(sock, buf, l);
+        if(1 != canberead(sock)) continue;
+        int n = read(sock, buf, BUFLEN-1);
+        if(n == 0){
+            WARNX("Server disconnected");
+            signals(0);
+        }
+        buf[n] = 0;
+        DBG("Got from server: %s", buf);
+        LOGMSG("Got from server: %s", buf);
+        l = process_server_message(buf, n);
+        if(l) sendmessage(sock, buf, l);
+    }
+}