3 files changed, 125 insertions, 0 deletions
diff --git a/03_exercise/echo_server/Makefile b/03_exercise/echo_server/Makefile
new file mode 100644
index 0000000..df023d1
--- /dev/null
+++ b/03_exercise/echo_server/Makefile
@@ -0,0 +1,22 @@
+#!/usr/bin/make
+.SUFFIXES:
+.PHONY: all run clean
+.SILENT: run
+
+TAR = client server
+CFLAGS = -c -Os -Wall -Werror
+
+%.o: %.c
+	$(CC) $(CFLAGS) $^ -o $@
+
+%: %.o
+	$(CC) -o $@ $^
+
+all: $(TAR)
+
+run: all
+	./server&
+	./client
+
+clean:
+	$(RM) $(RMFILES) $(TAR) *.o
diff --git a/03_exercise/echo_server/client.c b/03_exercise/echo_server/client.c
new file mode 100644
index 0000000..a664221
--- /dev/null
+++ b/03_exercise/echo_server/client.c
@@ -0,0 +1,47 @@
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <unistd.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+
+static inline void die(const char* msg)
+{
+	perror(msg);
+	exit(-1);
+}
+
+int main()
+{
+	struct sockaddr_in addr = {
+		.sin_family = AF_INET,
+		.sin_port = htons(8000),
+		.sin_addr.s_addr = inet_addr("127.0.0.1")
+	};
+	char buf[256];
+	int cfd;
+	
+	if ((cfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
+		die("Couldn't open the socket");
+	
+	if (connect(cfd, (struct sockaddr*) &addr, sizeof(addr)) < 0)
+		die("Couldn't connect to socket");
+	
+	for (int i = 0; i < 5; ++i)
+	{
+		if (write(cfd, "Ping", 4) < 0)
+			die("Couldn't send message");
+		
+		printf("[send] Ping\n");
+		
+		if (read(cfd, buf, sizeof(buf)) < 0)
+			die("Couldn't receive message");
+		
+		printf("[recv] %s\n", buf);
+	}
+	
+	close(cfd);
+	return 0;
+}
diff --git a/03_exercise/echo_server/server.c b/03_exercise/echo_server/server.c
new file mode 100644
index 0000000..faf309c
--- /dev/null
+++ b/03_exercise/echo_server/server.c
@@ -0,0 +1,56 @@
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <unistd.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+
+static inline void die(const char* msg)
+{
+	perror(msg);
+	exit(-1);
+}
+
+int main()
+{
+	struct sockaddr_in srv_addr, cli_addr;
+	int sockopt = 1;
+	socklen_t sad_sz = sizeof(struct sockaddr_in);
+	int sfd, cfd;
+	ssize_t bytes;
+	char buf[256];
+	
+	srv_addr.sin_family = AF_INET;
+	srv_addr.sin_port = htons(8000);
+	srv_addr.sin_addr.s_addr = INADDR_ANY;
+	
+	if ((sfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
+		die("Couldn't open the socket");
+	
+	setsockopt(sfd, SOL_SOCKET, SO_REUSEADDR, (char*) &sockopt, sizeof(sockopt));
+	
+	if (bind(sfd, (struct sockaddr*) &srv_addr, sad_sz) < 0)
+		die("Couldn't bind socket");
+	
+	if (listen(sfd, 1) < 0)
+		die("Couldn't listen to the socket");
+	
+	cfd = accept(sfd, (struct sockaddr*) &cli_addr, &sad_sz);
+	if (cfd < 0)
+		die("Couldn't accept incoming connection");
+	
+	while ((bytes = read(cfd, buf, sizeof(buf))) != 0)
+	{
+		if (bytes < 0)
+			die("Couldn't receive message");
+		
+		if (write(cfd, buf, bytes) < 0)
+			die("Couldn't send message");
+	}
+	
+	close(cfd);
+	close(sfd);
+	return 0;
+}