basic socket server

server.cpp

@@ -1,6 +1,263 @@
 #include "user.h"
 
+#include <cstddef>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <filesystem>
+
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <signal.h>
+
+#define BUF 1024
+
+namespace fs = std::filesystem;
+
+int abortRequested = 0;
+int create_socket = -1;
+int new_socket = -1;
+
+void printUsage();
+inline bool isInteger(const std::string & s);
+
+// from myserver.c
+void *clientCommunication(void *data);
+void signalHandler(int sig);
+
 int main (int argc, char* argv[])
 {
-	//
+	if (argc < 3 ||	
+		!isInteger(argv[1]) ||
+		!fs::is_directory(argv[2])
+		) {
+		printUsage();
+		return EXIT_FAILURE;
+	}
+
+	char* p;
+	u_long PORT = strtoul(argv[1], &p, 10);
+
+	/* Code largely from the client-server-sample git / myserver.c */
+
+	__socklen_t addrlen;
+	struct sockaddr_in address, cliaddress;
+	int reuseValue = 1;
+
+	if (signal(SIGINT, signalHandler) == SIG_ERR) {
+		perror("signal can not be registered");
+		return EXIT_FAILURE;
+	}
+
+	if ((create_socket = socket(AF_INET, SOCK_STREAM, 0)) == -1)
+	{
+		perror("Socket error"); // errno set by socket()
+		return EXIT_FAILURE;
+	}
+
+	if (setsockopt(create_socket,
+						SOL_SOCKET,
+						SO_REUSEADDR,
+						&reuseValue,
+						sizeof(reuseValue)) == -1)
+	{
+		perror("set socket options - reuseAddr");
+		return EXIT_FAILURE;
+	}
+
+	if (setsockopt(create_socket,
+						SOL_SOCKET,
+						SO_REUSEPORT,
+						&reuseValue,
+						sizeof(reuseValue)) == -1)
+	{
+		perror("set socket options - reusePort");
+		return EXIT_FAILURE;
+	}
+
+	memset(&address, 0, sizeof(address));
+	address.sin_family = AF_INET;
+	address.sin_addr.s_addr = INADDR_ANY;
+	address.sin_port = htons(PORT);
+
+	if (bind(create_socket, (struct sockaddr *)&address, sizeof(address)) == -1)
+	{
+		perror("bind error");
+		return EXIT_FAILURE;
+	}
+
+	if (listen(create_socket, 5) == -1)
+	{
+		perror("listen error");
+		return EXIT_FAILURE;
+	}
+
+	while (!abortRequested)
+	{
+
+		printf("Waiting for connections...\n");
+
+		addrlen = sizeof(struct sockaddr_in);
+		if ((new_socket = accept(create_socket,
+										 (struct sockaddr *)&cliaddress,
+										 &addrlen)) == -1)
+		{
+			if (abortRequested)
+			{
+				perror("accept error after aborted");
+			}
+			else
+			{
+				perror("accept error");
+			}
+			break;
+		}
+
+		printf("Client connected from %s:%d...\n",
+				 inet_ntoa(cliaddress.sin_addr),
+				 ntohs(cliaddress.sin_port));
+		clientCommunication(&new_socket); // returnValue can be ignored
+		new_socket = -1;
+	}
+
+
+	if (create_socket != -1)
+	{
+		if (shutdown(create_socket, SHUT_RDWR) == -1)
+		{
+			perror("shutdown create_socket");
+		}
+		if (close(create_socket) == -1)
+		{
+			perror("close create_socket");
+		}
+		create_socket = -1;
+	}
+
+	return EXIT_SUCCESS;
+
+}
+
+// https://stackoverflow.com/questions/2844817/how-do-i-check-if-a-c-string-is-an-int
+inline bool isInteger(const std::string & s)
+{
+	if(s.empty() || ((!isdigit(s[0])) && (s[0] != '-') && (s[0] != '+'))) return false;
+
+	char * p;
+	strtol(s.c_str(), &p, 10);
+
+	return (*p == 0);
+}
+
+void printUsage()
+{
+	printf("printUsage\n");
+}
+
+void *clientCommunication(void *data)
+{
+	char buffer[BUF];
+	int size;
+	int *current_socket = (int *)data;
+
+	strcpy(buffer, "Welcome to myserver!\r\nPlease enter your commands...\r\n");
+	if (send(*current_socket, buffer, strlen(buffer), 0) == -1) {
+		perror("send failed");
+		return NULL;
+	}
+
+	do {
+		size = recv(*current_socket, buffer, BUF - 1, 0);
+		if (size == -1) {
+			if (abortRequested) {
+				perror("recv error after aborted");
+			} else {
+				perror("recv error");
+			}
+			break;
+		}
+
+		if (size == 0) {
+			printf("Client closed remote socket\n"); // ignore error
+			break;
+		}
+
+		// remove ugly debug message, because of the sent newline of client
+		if (buffer[size - 2] == '\r' && buffer[size - 1] == '\n')
+		{
+			size -= 2;
+		}
+		else if (buffer[size - 1] == '\n')
+		{
+			--size;
+		}
+
+		buffer[size] = '\0';
+		printf("Message received: %s\n", buffer); // ignore error
+
+		if (send(*current_socket, "OK", 3, 0) == -1)
+		{
+			perror("send answer failed");
+			return NULL;
+		}
+	} while (strcmp(buffer, "quit") != 0 && !abortRequested);
+
+	// closes/frees the descriptor if not already
+	if (*current_socket != -1)
+	{
+		if (shutdown(*current_socket, SHUT_RDWR) == -1)
+		{
+			perror("shutdown new_socket");
+		}
+		if (close(*current_socket) == -1)
+		{
+			perror("close new_socket");
+		}
+		*current_socket = -1;
+	}
+
+	return NULL;
+}
+
+void signalHandler(int sig)
+{
+	if (sig == SIGINT)
+	{
+		printf("abort Requested... "); // ignore error
+		abortRequested = 1;
+		/////////////////////////////////////////////////////////////////////////
+		// With shutdown() one can initiate normal TCP close sequence ignoring
+		// the reference count.
+		// https://beej.us/guide/bgnet/html/#close-and-shutdownget-outta-my-face
+		// https://linux.die.net/man/3/shutdown
+		if (new_socket != -1)
+		{
+			if (shutdown(new_socket, SHUT_RDWR) == -1)
+			{
+				perror("shutdown new_socket");
+			}
+			if (close(new_socket) == -1)
+			{
+				perror("close new_socket");
+			}
+			new_socket = -1;
+		}
+
+		if (create_socket != -1)
+		{
+			if (shutdown(create_socket, SHUT_RDWR) == -1)
+			{
+				perror("shutdown create_socket");
+			}
+			if (close(create_socket) == -1)
+			{
+				perror("close create_socket");
+			}
+			create_socket = -1;
+		}
+	}
+	else
+	{
+		exit(sig);
+	}
 }