Don't call memcpy() if there is nothing to copy

- rename "flag_connection_alive" variable back to "global_connection_alive"
- return exit code from run_terminal_mode()
- rcon_command(): add error messages

BUILDING.md

@@ -0,0 +1,29 @@
+Building and installing
+-----------------------
+
+#### Requirements & dependencies:
+- GCC compatible compiler
+- POSIX getopt support from **<unistd.h>**
+
+---
+
+#### Compiling
+
+    cc -std=gnu99 -Wpedantic -Wall -Wextra -Wno-gnu-zero-variadic-macro-arguments -O2 -o mcrcon mcrcon.c
+    
+>[!NOTE]
+>If you are compiling on Windows remember to link with winsock by adding `-lws2_32` to your compiler command line.
+
+---
+
+Or you can run **make**
+
+    make           - compiles mcrcon
+    make install   - installs compiled binaries and manpage to the system
+    make uninstall - removes binaries and manpage from the system
+    
+    file install locations:
+        /usr/local/bin/mcrcon
+        /usr/local/share/man/man1/mcrcon.1
+
+Makefile **install** and **uninstall** rules are not available on Windows.

CHANGELOG.md

@@ -3,6 +3,10 @@
 ###### 0.7.3
  - Add support to Valve style rcon authentication
  - Change maximum packet size to correct value (4096 -> 4106)
+ - Print auth failed message to stderr instead of stdout
+ - Fail immediately if received packet size is out of spec
+ - Return proper exit code from run_terminal_mode()
+ - Add error messages to rcon_command() function
  
 ###### 0.7.2
  - Quit gracefully when Ctrl-D or Ctrl+C is pressed

INSTALL.md

@@ -1,22 +0,0 @@
-Building and installing
------------------------
-
-Only dependency is C library and POSIX getopt support. 
-
-Compiling with GCC or CLANG:
-
-    cc -std=gnu99 -Wpedantic -Wall -Wextra -O2 -o mcrcon mcrcon.c
-    
-Note: on Windows remember to link with winsock by adding `-lws2_32` to your compiler command line.
-
-Or you can just run "**make**":
-
-    make           - compiles mcrcon
-    make install   - installs compiled binaries and manpage to the system
-    make uninstall - removes binaries and manpage from the system
-    
-    file install locations:
-        /usr/local/bin/mcrcon
-        /usr/local/share/man/man1/mcrcon.1
-
-Makefile "**install**" and "**uninstall**" rules are disabled on windows.

Makefile

@@ -13,8 +13,8 @@ INSTALL = install
 LINKER =
 RM = rm -v -f
 
-CC = gcc
-CFLAGS = -std=gnu99 -Wall -Wextra -Wpedantic -O2
+CC ?= gcc
+CFLAGS = -std=gnu99 -Wall -Wextra -Wpedantic -Wno-gnu-zero-variadic-macro-arguments -O2
 EXTRAFLAGS ?= -fstack-protector-all
 
 ifeq ($(OS), Windows_NT)
@@ -44,4 +44,4 @@ endif
 
 .PHONY: clean
 clean:
-	$(RM) $(EXENAME)
+	$(RM) $(EXENAME) $(EXENAME).exe

README.md

@@ -1,6 +1,9 @@
 # mcrcon
 
-mcrcon is console based Minecraft [rcon](https://developer.valvesoftware.com/wiki/Source_RCON_Protocol) client for remote administration and server maintenance scripts.
+mcrcon is a command-line [rcon](https://developer.valvesoftware.com/wiki/Source_RCON_Protocol) client intended for remote server administration and maintenance automation.
+
+Though originally developed for Minecraft servers, it also works with a variety of other servers using the Valve or Minecraft-style rcon protocol.
+
 
 ---
 
@@ -29,7 +32,7 @@ make
 # install is optional
 sudo make install
 ```
-Check [INSTALL.md](INSTALL.md) for more details.
+_Check [BUILDING.md](BUILDING.md) for more details._
 
 ---
 
@@ -68,17 +71,15 @@ Send three commands ("say", "save-all", "stop") and wait five seconds between th
 ```sh
 mcrcon -H my.minecraft.server -p password -w 5 "say Server is restarting!" save-all stop
 ```
-
 ---
 
-##### How to enable rcon on a Minecraft Server 
-
-Enable rcon by adding following lines to [```server.properties```](https://minecraft.gamepedia.com/Server.properties) configuration file.
-```
-enable-rcon=true
-rcon.port=25575
-rcon.password=your_rcon_pasword
-```
+> [!TIP]
+>Enable RCON on Minecraft server by adding following lines to [```server.properties```](https://minecraft.gamepedia.com/Server.properties) configuration file.
+>```
+>enable-rcon=true
+>rcon.port=25575
+>rcon.password=your_rcon_pasword
+>```
 
 ---
 
@@ -88,16 +89,17 @@ rcon.password=your_rcon_pasword
 * MAIL:           tiiffi+mcrcon at gmail
 * ISSUES:         https://github.com/Tiiffi/mcrcon/issues/
 
-When reporting issues, please provide the following information:
-
-- Version of mcrcon: Please specify the precise version number
-- Game: Indicate the specific game server you're using (e.g., Minecraft, Valve Source Engine game, ARK, ...)
-- Server version: Provide the exact version of the game server
-- Mods and Extensions: List all mods and extensions used, including their versions
-- Issue Description: Clearly describe the problem you're encountering and the expected behavior.
-- Steps to reproduce
-
-If you're tech-savvy, consider providing a packet capture file (PCAP). Remember to use a fake password.
+> [!TIP]
+>When reporting issues, please provide the following information:
+>
+>- Version of mcrcon: Please specify the precise version number
+>- Game: Indicate the specific game server you're using (e.g., Minecraft, Valve Source Engine game, ARK, ...)
+>- Server version: Provide the exact version of the game server
+>- Mods and Extensions: List all mods and extensions used, including their versions
+>- Issue Description: Clearly describe the problem you're encountering and the expected behavior.
+>- Steps to reproduce
+>
+>If you're tech-savvy, consider providing a packet capture file (PCAP). Remember to use a fake password.
 
 ---
 

mcrcon.1

@@ -11,7 +11,7 @@ options
 commands
 .B ]
 .SH DESCRIPTION
-mcrcon is Minecraft rcon client for remote administration and server maintenance scripts.
+mcrcon is a command-line rcon client intended for remote server administration and maintenance automation.
 .SH OPTIONS
 .IP -H
 Server address (default: localhost)

mcrcon.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012-2021, Tiiffi <tiiffi at gmail>
+ * Copyright (c) 2012-2024, Tiiffi <tiiffi at gmail>
  *
  * This software is provided 'as-is', without any express or implied
  * warranty. In no event will the authors be held liable for any damages
@@ -24,26 +24,20 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdint.h>
+#include <stdbool.h>
 #include <string.h>
 #include <strings.h>
 #include <signal.h>
 #include <errno.h>
 #include <unistd.h>
-#include <limits.h>
+
 
 #ifdef _WIN32
-    // for name resolving on windows
-    // enable this if you get compiler whine about getaddrinfo() on windows
-    //#define _WIN32_WINNT 0x0501
-
-    #include <ws2tcpip.h>
 	#include <winsock2.h>
     #include <windows.h>
+    #include <ws2tcpip.h>
 #else
-    #include <sys/types.h>
     #include <sys/socket.h>
-    #include <netinet/in.h>
-    #include <arpa/inet.h>
     #include <netdb.h>
 #endif
 
@@ -57,20 +51,22 @@
 #define RCON_AUTH_RESPONSE      2
 #define RCON_PID                0xBADC0DE
 
-#define DATA_BUFFSIZE   4096
-#define MAX_PACKET_SIZE 4106
-#define MIN_PACKET_SIZE 10
+#define MAX_COMMAND_LENGTH 	4096
+#define DATA_BUFFSIZE		MAX_COMMAND_LENGTH + 2 // plus two null terminators
+#define MAX_PACKET_SIZE		4106 // id (4) + cmd (4) + DATA_BUFFSIZE
+#define MIN_PACKET_SIZE		10   // id (4) + cmd (4) + two empty strings (2)
+
+#define log_error(fmt, ...) fprintf(stderr, fmt,  ##__VA_ARGS__);
 
 // rcon packet structure
-typedef struct _rc_packet {
-    int size;
-    int id;
-    int cmd;
-    char data[DATA_BUFFSIZE];
+typedef struct {
+    int32_t size;
+    int32_t id;
+    int32_t cmd;
+    uint8_t data[DATA_BUFFSIZE];
     // ignoring string2 for now
 } rc_packet;
 
-
 // ===================================
 //  FUNCTION DEFINITIONS              
 // ===================================
@@ -81,10 +77,8 @@ void        net_init_WSA(void);
 #endif
 void        net_close(int sd);
 int         net_connect(const char *host, const char *port);
-int         net_send(int sd, const uint8_t *buffer, size_t size);
-int         net_send_packet(int sd, rc_packet *packet);
+bool        net_send_packet(int sd, rc_packet *packet);
 rc_packet*  net_recv_packet(int sd);
-int         net_clean_incoming(int sd, int size);
 
 // Misc stuff
 void        usage(void);
@@ -96,21 +90,21 @@ int         run_terminal_mode(int sock);
 int         run_commands(int argc, char *argv[]);
 
 // Rcon protocol related functions
-rc_packet*  packet_build(int id, int cmd, char *s1);
+rc_packet*  packet_build(int id, int cmd, char s[static 1]);
 void        packet_print(rc_packet *packet);
-int         rcon_auth(int sock, char *passwd);
+bool        rcon_auth(int sock, char *passwd);
 int         rcon_command(int sock, char *command);
 
 
 // =============================================
 //  GLOBAL VARIABLES
 // =============================================
-static int global_raw_output = 0;
-static int global_silent_mode = 0;
-static int global_disable_colors = 0;
+static int flag_raw_output = 0;
+static int flag_silent_mode = 0;
+static int flag_disable_colors = 0;
+static int flag_wait_seconds = 0;
 static int global_connection_alive = 1;
 static int global_rsock;
-static int global_wait_seconds = 0;
 
 #ifdef _WIN32
   // console coloring on windows
@@ -124,7 +118,7 @@ void exit_proc(void)
 		net_close(global_rsock);
 }
 
-// Check windows & linux behaviour !!!
+// TODO: check exact windows and linux behaviour
 void sighandler(int sig)
 {
 	if (sig == SIGINT)
@@ -144,17 +138,17 @@ unsigned int mcrcon_parse_seconds(char *str)
 	long result = strtol(str, &end, 10);
 
 	if (errno != 0) {
-		fprintf(stderr, "-w invalid value.\nerror %d: %s\n", errno, strerror(errno));
+		log_error("-w invalid value.\nerror %d: %s\n", errno, strerror(errno));
 		exit(EXIT_FAILURE);
 	}
 
 	if (end == str) {
-		fprintf(stderr, "-w invalid value (not a number?)\n");
+		log_error("-w invalid value (not a number?)\n");
 		exit(EXIT_FAILURE);
 	}
 
 	if (result <= 0 || result > MAX_WAIT_TIME) {
-		fprintf(stderr, "-w value out of range.\nAcceptable value is 1 - %d (seconds).\n", MAX_WAIT_TIME);
+		log_error("-w value out of range.\nAcceptable value is 1 - %d (seconds).\n", MAX_WAIT_TIME);
 		exit(EXIT_FAILURE);
 	}
 
@@ -187,17 +181,17 @@ int main(int argc, char *argv[])
 			case 'H': host = optarg;                 break;
 			case 'P': port = optarg;                 break;
 			case 'p': pass = optarg;                 break;
-			case 'c': global_disable_colors = 1;    break;
-			case 's': global_silent_mode = 1;       break;
+			case 'c': flag_disable_colors = 1;       break;
+			case 's': flag_silent_mode = 1;          break;
 			case 'i': /* reserved for interp mode */ break;
 			case 't': terminal_mode = 1;             break;
-			case 'r': global_raw_output = 1;        break;
+			case 'r': flag_raw_output = 1;           break;
 			case 'w':
-				global_wait_seconds = mcrcon_parse_seconds(optarg);
+				flag_wait_seconds = mcrcon_parse_seconds(optarg);
 			break;
 
 			case 'v':
-				puts(VER_STR" - https://github.com/Tiiffi/mcrcon");
+				puts(VER_STR);
 				puts("Bug reports:\n\ttiiffi+mcrcon at gmail\n\thttps://github.com/Tiiffi/mcrcon/issues/");
 				exit(EXIT_SUCCESS);
 
@@ -214,8 +208,9 @@ int main(int argc, char *argv[])
 		exit(EXIT_FAILURE);
 	}
 
-	if(optind == argc && terminal_mode == 0)
+	if(optind == argc && terminal_mode == 0) {
 		terminal_mode = 1;
+	}
 
 	// safety features to prevent "IO: Connection reset" bug on the server side
 	atexit(&exit_proc);
@@ -237,13 +232,11 @@ int main(int argc, char *argv[])
 
 	// auth & commands
 	if (rcon_auth(global_rsock, pass)) {
-		if (terminal_mode)
-			run_terminal_mode(global_rsock);
-		else
-			exit_code = run_commands(argc, argv);
+		if (terminal_mode) exit_code = run_terminal_mode(global_rsock);
+		else exit_code = run_commands(argc, argv);
 	}
 	else { // auth failed
-		fprintf(stdout, "Authentication failed!\n");
+		log_error("Authentication failed!\n");
 		exit_code = EXIT_FAILURE;
 	}
 
@@ -298,7 +291,7 @@ void net_init_WSA(void)
 
 	int err = WSAStartup(version, &wsadata);
 	if (err != 0) {
-		fprintf(stderr, "WSAStartup failed. Error: %d.\n", err);
+		log_error("WSAStartup failed. Error: %d.\n", err);
 		exit(EXIT_FAILURE);
 	}
 }
@@ -315,7 +308,6 @@ void net_close(int sd)
 	#endif
 }
 
-// Opens and connects socket
 // http://man7.org/linux/man-pages/man3/getaddrinfo.3.html
 // https://bugs.chromium.org/p/chromium/issues/detail?id=44489
 int net_connect(const char *host, const char *port)
@@ -336,11 +328,11 @@ int net_connect(const char *host, const char *port)
 
 	int ret = getaddrinfo(host, port, &hints, &server_info);
 	if (ret != 0) {
-		fprintf(stderr, "Name resolution failed.\n");
+		log_error("Name resolution failed.\n");
 		#ifdef _WIN32
-			fprintf(stderr, "Error %d: %s", ret, gai_strerror(ret));
+			log_error("Error %d: %s", ret, gai_strerror(ret));
 		#else
-			fprintf(stderr, "Error %d: %s\n", ret, gai_strerror(ret));
+			log_error("Error %d: %s\n", ret, gai_strerror(ret));
 		#endif
 
 		exit(EXIT_FAILURE);
@@ -364,9 +356,9 @@ int net_connect(const char *host, const char *port)
 
 	if (p == NULL) {
 		/* TODO (Tiiffi): Check why windows does not report errors */
-		fprintf(stderr, "Connection failed.\n");
+		log_error("Connection failed.\n");
 		#ifndef _WIN32
-			fprintf(stderr, "Error %d: %s\n", errno, strerror(errno));
+			log_error("Error %d: %s\n", errno, strerror(errno));
 		#endif
 
 		freeaddrinfo(server_info);
@@ -377,82 +369,59 @@ int net_connect(const char *host, const char *port)
 	return sd;
 }
 
-int net_send(int sd, const uint8_t *buff, size_t size)
+bool net_send_packet(int sd, rc_packet *packet)
 {
 	size_t sent = 0;
+	size_t size = packet->size + sizeof(int32_t);
 	size_t left = size;
 
-	while (sent < size) {
-		int result = send(sd, (const char *) buff + sent, left, 0);
+	char *p = (char *) packet;
 
-		if (result == -1)
-			return -1;
+	while (sent < size) {
+		ssize_t result = send(sd, p + sent, left, 0);
+
+		if (result == -1) return false;
 
 		sent += result;
 		left -= sent;
 	}
 
-	return 0;
-}
-
-int net_send_packet(int sd, rc_packet *packet)
-{
-	int len;
-	int total = 0;	// bytes we've sent
-	int bytesleft;	// bytes left to send 
-	int ret = -1;
-
-	bytesleft = len = packet->size + sizeof(int);
-
-	while (total < len) {
-		ret = send(sd, (char *) packet + total, bytesleft, 0);
-		if(ret == -1) break;
-		total += ret;
-		bytesleft -= ret;
-	}
-
-	return ret == -1 ? -1 : 1;
+	return true;
 }
 
 rc_packet *net_recv_packet(int sd)
 {
-	int psize;
-	static rc_packet packet = {0, 0, 0, { 0x00 }};
+	int32_t psize;
+	static rc_packet packet = {0};
 
-	// packet.size = packet.id = packet.cmd = 0;
-
-	int ret = recv(sd, (char *) &psize, sizeof(int), 0);
+	ssize_t ret = recv(sd, (char *) &psize, sizeof(psize), 0);
 
 	if (ret == 0) {
-		fprintf(stderr, "Connection lost.\n");
+		log_error("Connection lost.\n");
 		global_connection_alive = 0;
 		return NULL;
 	}
 
-	if (ret != sizeof(int)) {
-		fprintf(stderr, "Error: recv() failed. Invalid packet size (%d).\n", ret);
+	if (ret != sizeof(psize)) {
+		log_error("Error: recv() failed.\n");
 		global_connection_alive = 0;
 		return NULL;
 	}
 
-	// NOTE(Tiiffi): This should fail if size is out of spec!
 	if (psize < MIN_PACKET_SIZE || psize > MAX_PACKET_SIZE) {
-		fprintf(stderr, "Warning: invalid packet size (%d). Must over 10 and less than %d.\n", psize, MAX_PACKET_SIZE);
-
-		// WARNING(Tiiffi): This is probably not the way to go. Probably should just fail and exit.
-		if(psize > MAX_PACKET_SIZE || psize < 0) psize = MAX_PACKET_SIZE;
-		net_clean_incoming(sd, psize);
-
+		log_error("Error: Invalid packet size (%d).\n", psize);
+		global_connection_alive = 0;
 		return NULL;
 	}
 
 	packet.size = psize;
+	char *p = (char *) &packet;
 
 	int received = 0;
 	while (received < psize) {
-		ret = recv(sd, (char *) &packet + sizeof(int) + received, psize - received, 0);
+		ret = recv(sd, p + sizeof(int32_t) + received, psize - received, 0);
 		if (ret == 0) {
-			fprintf(stderr, "Connection lost.\n");
+			log_error("Connection lost.\n");
 			global_connection_alive = 0;
 			return NULL;
 		}
@@ -463,19 +432,6 @@ rc_packet *net_recv_packet(int sd)
 	return &packet;
 }
 
-int net_clean_incoming(int sd, int size)
-{
-	char tmp[size];
-	int ret = recv(sd, tmp, size, 0);
-
-	if(ret == 0) {
-		fprintf(stderr, "Connection lost.\n");
-		global_connection_alive = 0;
-	}
-
-	return ret;
-}
-
 void print_color(int color)
 {
 	// sh compatible color array
@@ -500,8 +456,9 @@ void print_color(int color)
 		"\033[4m"       /* 16 UNDERLINE 0x6e */
 	};
 
-	/* 0x72: 'r' */
-	if (color == 0 || color == 0x72) fputs("\033[0m", stdout); /* CANCEL COLOR */
+	if (color == 0 || color == 0x72) {
+		fputs("\033[0m", stdout); // cancel color
+	}
 	else
 	#endif
 	{
@@ -509,7 +466,7 @@ void print_color(int color)
 		else if (color >= 0x30 && color <= 0x39)
 			color -= 0x30;
 		else if (color == 0x6e)
-			color = 16; /* 0x6e: 'n' */
+			color = 16;
 		else return;
 
 		#ifndef _WIN32
@@ -523,85 +480,89 @@ void print_color(int color)
 // this hacky mess might use some optimizing
 void packet_print(rc_packet *packet)
 {
-	if (global_raw_output == 1) {
-		for (int i = 0; packet->data[i] != 0; ++i)
-			putchar(packet->data[i]);
+	uint8_t *data = packet->data;
 
+	if (flag_raw_output == 1) {
+		for (int i = 0; data[i] != 0; ++i) {
+			putchar(data[i]);
+		}
 		return;
 	}
 
 	int i;
-	int def_color = 0;
+	int default_color = 0;
 
 	#ifdef _WIN32
 		CONSOLE_SCREEN_BUFFER_INFO console_info;
 		if (GetConsoleScreenBufferInfo(console_handle, &console_info) != 0) {
-			def_color = console_info.wAttributes + 0x30;
-		} else def_color = 0x37;
+			default_color = console_info.wAttributes + 0x30;
+		} else default_color = 0x37;
 	#endif
 
 	// colors enabled so try to handle the bukkit colors for terminal
-	if (global_disable_colors == 0) {
-		for (i = 0; (unsigned char) packet->data[i] != 0; ++i) {
-			if (packet->data[i] == 0x0A) print_color(def_color);
-			else if((unsigned char) packet->data[i] == 0xc2 && (unsigned char) packet->data[i+1] == 0xa7) {
-				print_color(packet->data[i+=2]);
+	if (flag_disable_colors == 0) {
+		for (i = 0; data[i] != 0; ++i) {
+			if (data[i] == 0x0A) print_color(default_color);
+			else if(data[i] == 0xc2 && data[i + 1] == 0xa7) {
+				i += 2;
+				print_color(data[i]);
 				continue;
 			}
-			putchar(packet->data[i]);
+			putchar(data[i]);
 		}
-		print_color(def_color); // cancel coloring
+		print_color(default_color); // cancel coloring
 	}
 	// strip colors
 	else {
-		for (i = 0; (unsigned char) packet->data[i] != 0; ++i) {
-			if ((unsigned char) packet->data[i] == 0xc2 && (unsigned char) packet->data[i+1] == 0xa7) {
+		for (i = 0; data[i] != 0; ++i) {
+			if (data[i] == 0xc2 && data[i + 1] == 0xa7) {
 				i += 2;
 				continue;
 			}	
-			putchar(packet->data[i]);
+			putchar(data[i]);
 		}
 	}
 
 	// print newline if string has no newline
-	if (packet->data[i-1] != 10 && packet->data[i-1] != 13) putchar('\n');
+	if (data[i - 1] != 10 && data[i - 1] != 13) {
+		putchar('\n');
+	}
 }
 
-rc_packet *packet_build(int id, int cmd, char *s1)
+rc_packet *packet_build(int id, int cmd, char s[static 1])
 {
-	static rc_packet packet = {0, 0, 0, { 0x00 }};
+	static rc_packet packet = {0};
 
-	// NOTE(Tiiffi): Issue report states that outgoing payload has max size of 1460 bytes:
+	// NOTE(Tiiffi): Issue report states that maximum command packet size is 1460 bytes:
 	//				 https://github.com/Tiiffi/mcrcon/issues/45#issuecomment-1000940814
 	//				 https://mctools.readthedocs.io/en/master/rcon.html
 	//				 Have to do some testing to confirm!
 
-	// size + id + cmd + s1 + s2 NULL terminator
-	int len = strlen(s1);
-	if (len >= DATA_BUFFSIZE) {
-		fprintf(stderr, "Warning: Command string too long (%d). Maximum allowed: %d.\n", len, DATA_BUFFSIZE - 1);
+	int len = strlen(s);
+	if (len > MAX_COMMAND_LENGTH) {
+		log_error("Warning: Command string too long (%d). Maximum allowed: %d.\n", len, MAX_COMMAND_LENGTH);
 		return NULL;
 	}
 
-	packet.size = sizeof(int) * 2 + len + 2;
+	packet.size = sizeof packet.id + sizeof packet.cmd + len + 2;
 	packet.id = id;
 	packet.cmd = cmd;
-	strncpy(packet.data, s1, DATA_BUFFSIZE - 1);
+	if (packet.size > 0) memcpy(packet.data, s, len);
+	packet.data[len] = 0;
+	packet.data[len + 1] = 0;
 
 	return &packet;
 }
 
-int rcon_auth(int sock, char *passwd)
+bool rcon_auth(int sock, char *passwd)
 {
-	int ret;
-
 	rc_packet *packet = packet_build(RCON_PID, RCON_AUTHENTICATE, passwd);
 	if (packet == NULL)
 		return 0;
 
-	ret = net_send_packet(sock, packet);
-	if (!ret)
+	if (!net_send_packet(sock, packet)) {
 		return 0; // send failed
+	}
 
 receive:
 	packet = net_recv_packet(sock);
@@ -615,28 +576,36 @@ receive:
 		goto receive;
 	}
 
-	// return 1 if authentication OK
-	return packet->id == -1 ? 0 : 1;
+	// return true if authentication OK
+	return packet->id == -1 ? false : true;
 }
 
+// TODO: Add proper error handling and reporting!
 int rcon_command(int sock, char *command)
 {
 	rc_packet *packet = packet_build(RCON_PID, RCON_EXEC_COMMAND, command);
 	if (packet == NULL) {
-		global_connection_alive = 0;
+		log_error("Error: packet build() failed!\n");
 		return 0;
 	}
 
-	net_send_packet(sock, packet);
+	if (!net_send_packet(sock, packet)) {
+		log_error("Error: net_send_packet() failed!\n");
+		return 0;
+	}
 
 	packet = net_recv_packet(sock);
-	if (packet == NULL)
+	if (packet == NULL) {
+		log_error("Error: net_recv_packet() failed!\n");
 		return 0;
+	}
 
-	if (packet->id != RCON_PID)
+	if (packet->id != RCON_PID) {
+		log_error("Error: invalid packet id!\n");
 		return 0;
+	}
 
-	if (!global_silent_mode) {
+	if (!flag_silent_mode) {
 		if (packet->size > 10)
 		packet_print(packet);
 	}
@@ -652,38 +621,41 @@ int run_commands(int argc, char *argv[])
 		if (!rcon_command(global_rsock, argv[i]))
 			return EXIT_FAILURE;
 
-		if (++i >= argc)
+		i++;
+
+		if (i >= argc)
 			return EXIT_SUCCESS;
 
-		if (global_wait_seconds > 0) {
+		if (flag_wait_seconds > 0) {
 			#ifdef _WIN32
-				Sleep(global_wait_seconds * 1000);
+				Sleep(flag_wait_seconds * 1000);
 			#else
-				sleep(global_wait_seconds);
+				sleep(flag_wait_seconds);
 			#endif
 		}
 	}
 }
 
-// interactive terminal mode
+// terminal mode
 int run_terminal_mode(int sock)
 {
-	int ret = 0;
-	char command[DATA_BUFFSIZE] = {0};
+	char command[MAX_COMMAND_LENGTH] = {0};
 
 	puts("Logged in.\nType 'Q' or press Ctrl-D / Ctrl-C to disconnect.");
 
 	while (global_connection_alive) {
 		putchar('>');
 
-		int len = get_line(command, DATA_BUFFSIZE);
+		int len = get_line(command, MAX_COMMAND_LENGTH);
 		if (len < 1) continue; 
 	
-		if (strcasecmp(command, "Q") == 0)
-			break;
+		if (strcasecmp(command, "Q") == 0) break;
 
-		if (len > 0 && global_connection_alive)
-			ret += rcon_command(sock, command);
+		if (len > 0 && global_connection_alive) {
+			if (!rcon_command(sock, command)) {
+				return EXIT_FAILURE;
+			}
+		}
 
 		/* Special case for "stop" command to prevent server-side bug.
 		 * https://bugs.mojang.com/browse/MC-154617
@@ -695,11 +667,9 @@ int run_terminal_mode(int sock)
 		if (strcasecmp(command, "stop") == 0) {
 			break;
 		}
-
-		//command[0] = len = 0;
 	}
 
-	return ret;
+	return EXIT_SUCCESS;
 }
 
 // gets line from stdin and deals with rubbish left in the input buffer
@@ -708,7 +678,7 @@ int get_line(char *buffer, int bsize)
 	char *ret = fgets(buffer, bsize, stdin);
 	if (ret == NULL) {
 		if (ferror(stdin)) {
-			fprintf(stderr, "Error %d: %s\n", errno, strerror(errno));
+			log_error("Error %d: %s\n", errno, strerror(errno));
 			exit(EXIT_FAILURE);
 		}
 		putchar('\n');