diff --git a/Makefile b/Makefile
index 95a70e1..e49e931 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 
 
-all: bin/net bin/test
+all: bin/net bin/test bin/main
 
 
 bin/net: net.c
@@ -11,5 +11,9 @@ bin/test: test.c
 	mkdir -pv bin
 	gcc -o bin/test test.c
 
+bin/main: main.c
+	mkdir -pv bin
+	gcc -o bin/main main.c
+
 clean:
 	rm -rf bin
diff --git a/main.c b/main.c
new file mode 100644
index 0000000..47e9f59
--- /dev/null
+++ b/main.c
@@ -0,0 +1,79 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+
+#define MODE_SERVER 0
+#define MODE_CLIENT 1
+
+struct prog_info {
+	int mode;
+	int client_num;
+	int port;
+} prog_info;
+
+int parseArgs(struct prog_info *pinfo, int argc, char **argv) {
+	pinfo->mode = MODE_SERVER;
+	pinfo->client_num = 1;
+	pinfo->port = 4711;
+
+	if (argc <= 1) {
+		printf("usage: %s [-s|-c <num>] [-p <port>]\n", argv[0]);
+		return -1;
+	}
+	int i;
+	for (i=1; i<argc; i++) {
+		if (strncmp(argv[i], "-s", 2) == 0) {
+			pinfo->mode = MODE_SERVER;
+			continue;
+		}
+		if (strncmp(argv[i], "-c", 2) == 0) {
+			pinfo->mode = MODE_CLIENT;
+			if (argc <= i+1) {
+				printf("client number not specified\n");
+				return -2;
+			}
+			pinfo->client_num = (int)strtol(argv[++i], NULL, 10);
+			if (pinfo->client_num <= 0) {
+				printf("invalid client number!\n");
+				return -3;
+			}
+			continue;
+		}
+		if (strncmp(argv[i], "-p", 2) == 0) {
+			if (argc <= i+1) {
+				printf("port not specified\n");
+				return -4;
+			}
+			pinfo->port = (int)strtol(argv[++i], NULL, 10);
+			if (pinfo->port <= 0 || 65536 <= pinfo->port) {
+				printf("invalid port number!\n");
+				return -5;
+			}
+			continue;
+		}
+		printf("unknown argument %s\n", argv[i]);
+		return -6;
+	}
+
+	return 0;
+}
+
+int main(int argc, char **argv) {
+
+	int ret;
+	if ((ret = parseArgs(&prog_info, argc, argv)) == 0) {
+			
+		printf("port: %d\n", prog_info.port);
+		if (prog_info.mode == MODE_SERVER) {
+			printf("runnin in SERVER mode\n");
+			//  ...
+		} else {
+			printf("running in CLIENT mode, using client number %d\n", prog_info.client_num);
+			// ...
+		}
+
+		return 0;
+	}
+	return ret;
+}
+