TCP request to some port (here: 12489)

Author: alexander-naumov

sockets/TCP/nsclient.c

@@ -0,0 +1,65 @@
+#include <error.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/utsname.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <netdb.h>
+#include <string.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#define fatal(msg) {perror(msg);}
+
+int nsclient(char *host)
+{
+	int sock;
+	struct sockaddr_in servadd;
+	struct hostent *hp;
+	char nodename[200], servname[200];
+
+	if ((sock = socket(AF_INET, SOCK_STREAM, 0)) == -1)
+		fatal("socket");
+
+	bzero(&servadd, sizeof(servadd));
+
+	if ((hp = gethostbyname(host)) == NULL)
+		fatal("gethostbyname");
+   
+	servadd.sin_port = htons(12489);
+	servadd.sin_family = AF_INET;
+	bcopy(hp->h_addr, (struct sockaddr *)&servadd.sin_addr, hp->h_length);
+
+	int status;
+	if ((status = connect(sock, (struct sockaddr *)&servadd, sizeof(servadd))) != 0)
+		if(errno != ECONNREFUSED)
+			fatal("connect");
+   
+	getnameinfo((struct sockaddr *)&servadd, sizeof(servadd),
+		nodename, sizeof(nodename), servname, sizeof(servname), 0);
+
+	close(sock);
+	return status;
+}
+
+void usage()
+{
+	printf("USAGE:\t scan <IP_address>\n");
+	exit(1);
+}
+
+int main(int argc, char *argv[])
+{
+	if(argv[1] == NULL)
+        	usage();
+
+	if (nsclient(argv[1]) == 0)
+		printf("nsclient: running\n");
+	else
+		printf("nsclient: no_answer\n");
+
+	return 0;
+}
+
+