diff --git a/03_io_access/lib/io.c b/03_io_access/lib/io.c
index 8552713..874e33a 100644
--- a/03_io_access/lib/io.c
+++ b/03_io_access/lib/io.c
@@ -13,6 +13,7 @@ static struct gpiod_line *button_line = NULL;
 // Error handling function
 static int handle_error(const char *msg) {
     perror(msg);
+    cleanup_gpio()
     return -1;
 }
 
diff --git a/04_intro_to_sockets/Makefile b/04_intro_to_sockets/Makefile
index 393b7ba..116698d 100644
--- a/04_intro_to_sockets/Makefile
+++ b/04_intro_to_sockets/Makefile
@@ -1,10 +1,11 @@
+# Compiler and flags
 CC = gcc
 CFLAGS = -Wall -Ilib
-#LDFLAGS = -lgpiod
 
 # Directories
 SRCDIR = src
 LIBDIR = lib
+BINDIR = bin
 OBJDIR = obj
 
 # Source files
@@ -13,27 +14,26 @@ SRC_SOURCES = $(wildcard $(SRCDIR)/*.c)
 
 # Object files
 LIB_OBJECTS = $(LIB_SOURCES:$(LIBDIR)/%.c=$(OBJDIR)/%.o)
-SRC_OBJECTS = $(SRC_SOURCES:$(SRCDIR)/%.c=$(OBJDIR)/%.o)
 
-# Target executable
-TARGET = sockets
+# Executables
+EXECS = $(SRC_SOURCES:$(SRCDIR)/%.c=$(BINDIR)/%)
 
-# Create obj directory if it doesn't exist
+# Create necessary directories
 $(shell mkdir -p $(OBJDIR))
+$(shell mkdir -p $(BINDIR))
 
 # Rules
-all: $(TARGET)
+all: $(EXECS)
 
-$(TARGET): $(LIB_OBJECTS) $(SRC_OBJECTS)
-	$(CC) $(LIB_OBJECTS) $(SRC_OBJECTS) -o $@ $(LDFLAGS)
+$(BINDIR)/%: $(SRCDIR)/%.c $(LIB_OBJECTS)
+	$(CC) $(CFLAGS) -o $@ $< $(LIB_OBJECTS) 
 
 $(OBJDIR)/%.o: $(LIBDIR)/%.c
 	$(CC) $(CFLAGS) -c $< -o $@
 
-$(OBJDIR)/%.o: $(SRCDIR)/%.c
-	$(CC) $(CFLAGS) -c $< -o $@
-
 clean:
-	rm -f $(OBJDIR)/*.o $(TARGET)
+	rm -f $(OBJDIR)/*.o
+	rm -f $(BINDIR)/*
 
 .PHONY: all clean
+
diff --git a/04_intro_to_sockets/README.md b/04_intro_to_sockets/README.md
index efc3305..eb91d03 100644
--- a/04_intro_to_sockets/README.md
+++ b/04_intro_to_sockets/README.md
@@ -7,5 +7,5 @@ a LED, a button and a temperature sensor.
 
 ```bash
 $ make
-$ ./io
+$ ./sockets
 ```
diff --git a/04_intro_to_sockets/bin/daytimeTCPCli b/04_intro_to_sockets/bin/daytimeTCPCli
new file mode 100755
index 0000000..549cb11
Binary files /dev/null and b/04_intro_to_sockets/bin/daytimeTCPCli differ
diff --git a/04_intro_to_sockets/bin/daytimeTCPSrv b/04_intro_to_sockets/bin/daytimeTCPSrv
new file mode 100755
index 0000000..6d094af
Binary files /dev/null and b/04_intro_to_sockets/bin/daytimeTCPSrv differ
diff --git a/04_intro_to_sockets/lib/sockets.c b/04_intro_to_sockets/lib/sockets.c
index e69de29..7031a77 100644
--- a/04_intro_to_sockets/lib/sockets.c
+++ b/04_intro_to_sockets/lib/sockets.c
@@ -0,0 +1,113 @@
+#include <arpa/inet.h> // For inet_addr(), htons()
+#include <stdio.h> // For printf()
+#include <stdlib.h> // For exit()
+#include <string.h> // For memset() 
+#include <sys/socket.h> // For socket(), connect(), read(), write()
+#include <time.h>
+#include <unistd.h> // For close()
+#include "sockets.h"
+
+#define BUFFER_SIZE 1024
+
+static void error_handling(char *message, int sock) {
+    perror(message);
+    close(sock);
+    exit(1);
+}
+
+int tcp_create_socket() {
+    // PF_INET: IPv4, SOCK_STREAM: TCP
+    int sock = socket(PF_INET, SOCK_STREAM, 0); 
+    if (sock == -1)
+        error_handling("socket() error", sock);
+    return sock;
+}
+
+void connect_to_server(int sock, char *ip, int port) {
+    struct sockaddr_in serv_addr;
+    // Initialize serv_addr to zero
+    memset(&serv_addr, 0, sizeof(serv_addr));
+    // Set the address family to IPv4
+    serv_addr.sin_family = AF_INET;
+    // Convert IP address to binary form
+    serv_addr.sin_addr.s_addr = inet_addr(ip);
+    // Convert port number to network byte order
+    serv_addr.sin_port = htons(port);
+
+    if (connect(sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) == -1)
+        error_handling("connect() error", sock);
+}
+
+char* communicate(int sock, char *message) {
+    // Sending the ASCII string
+    if (write(sock, message, strlen(message)) == -1)
+        error_handling("write() error", sock);
+
+    // Receiving response
+    char* response = malloc(BUFFER_SIZE);
+    if (!response) 
+        error_handling("Failed to allocate memory for response", sock);
+
+    int str_len = read(sock, response, BUFFER_SIZE - 1);
+    if (str_len == -1){
+        free(response);
+        error_handling("read() error", sock);
+    } else if (str_len == 0) {
+        printf("Server closed the connection.\n");
+        free(response);
+        return NULL;
+    } else {
+        response[str_len] = '\0'; // Null-terminate the received data
+    }
+    return response;
+}
+
+int tcp_listen(int port) {
+    int sock = tcp_create_socket();
+
+    struct sockaddr_in serv_addr;
+    memset(&serv_addr, 0, sizeof(serv_addr));
+    serv_addr.sin_family = AF_INET;
+    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
+    serv_addr.sin_port = htons(port);
+
+    if (bind(sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) == -1)
+        error_handling("bind() error", sock);
+
+    if (listen(sock, 5) == -1)
+        error_handling("listen() error", sock);
+
+    return sock;
+}
+
+int tcp_accept(int serv_sock) {
+    struct sockaddr_in clnt_addr;
+    socklen_t clnt_addr_size = sizeof(clnt_addr);
+    int clnt_sock = accept(serv_sock, (struct sockaddr*)&clnt_addr, &clnt_addr_size);
+    if (clnt_sock == -1)
+        error_handling("accept() error", clnt_sock);
+    return clnt_sock;
+}
+
+void process_request(int clnt_sock) {
+    char message[BUFFER_SIZE];
+    int str_len = read(clnt_sock, message, BUFFER_SIZE - 1);
+    if (str_len == -1)
+        // TODO: clnt_sock might be a bug
+        error_handling("read() error", clnt_sock); 
+
+    message[str_len] = '\0'; // Null-terminate the string
+
+    time_t t = time(NULL);
+    struct tm *timeinfo;
+
+    if (strcmp(message, "1") == 0) {
+        timeinfo = localtime(&t); // Local time
+    } else {
+        timeinfo = gmtime(&t);    // GMT time
+    }
+
+    strftime(message, BUFFER_SIZE, "%Y-%m-%d %H:%M:%S", timeinfo);
+    write(clnt_sock, message, strlen(message));
+}
+
diff --git a/04_intro_to_sockets/lib/sockets.h b/04_intro_to_sockets/lib/sockets.h
index ab5885f..cf6322d 100644
--- a/04_intro_to_sockets/lib/sockets.h
+++ b/04_intro_to_sockets/lib/sockets.h
@@ -1,5 +1,22 @@
 #ifndef SOCKETS_LIB_H
 #define SOCKETS_LIB_H
 
+// Function to create a TCP socket
+int tcp_create_socket();
 
-#endif // SOCKETS_H
+// Function to connect to a server
+void connect_to_server(int sock, char *ip, int port);
+
+// Function to communicate with the server
+char* communicate(int sock, char *message);
+
+// Function to create a TCP server socket
+int tcp_listen(int port);
+
+// Function to accept a client connection
+int tcp_accept(int serv_sock);
+
+// Function to process a client request
+void process_request(int clnt_sock);
+
+#endif // SOCKETS_LIB_H
diff --git a/04_intro_to_sockets/obj/sockets.o b/04_intro_to_sockets/obj/sockets.o
new file mode 100644
index 0000000..a45d678
Binary files /dev/null and b/04_intro_to_sockets/obj/sockets.o differ
diff --git a/04_intro_to_sockets/src/daytimeTCPCli.c b/04_intro_to_sockets/src/daytimeTCPCli.c
new file mode 100644
index 0000000..93badde
--- /dev/null
+++ b/04_intro_to_sockets/src/daytimeTCPCli.c
@@ -0,0 +1,21 @@
+#include <stdio.h> // For printf()
+#include <unistd.h> // For close()
+#include <stdlib.h> // For exit(), atoi()
+#include "sockets.h"
+
+int main(int argc, char *argv[]) {
+    if (argc != 4) {
+        printf("Usage : %s <IP> <port> <message_to_send>\n", argv[0]);
+        exit(1);
+    }
+
+    int sock = tcp_create_socket();
+    connect_to_server(sock, argv[1], atoi(argv[2]));
+    char* received_data = communicate(sock, argv[3]);
+    if (received_data) {
+        printf("Received from server: %s\n", received_data);
+        free(received_data);
+    }
+    close(sock);
+    return 0;
+}
diff --git a/04_intro_to_sockets/src/daytimeTCPSrv.c b/04_intro_to_sockets/src/daytimeTCPSrv.c
new file mode 100644
index 0000000..634f84a
--- /dev/null
+++ b/04_intro_to_sockets/src/daytimeTCPSrv.c
@@ -0,0 +1,20 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include "sockets.h"
+
+int main(int argc, char *argv[]) {
+    if (argc != 2) {
+        printf("Usage: %s <port>\n", argv[0]);
+        exit(1);
+    }
+
+    int port = atoi(argv[1]);
+    int serv_sock = tcp_listen(port);
+    int clnt_sock = tcp_accept(serv_sock);
+
+    process_request(clnt_sock);
+    close(clnt_sock);
+    close(serv_sock);
+    return 0;
+}
diff --git a/04_intro_to_sockets/src/main.c b/04_intro_to_sockets/src/main.c
deleted file mode 100644
index 2b8c6ac..0000000
--- a/04_intro_to_sockets/src/main.c
+++ /dev/null
@@ -1,4 +0,0 @@
-
-int main() {
-    return 0;
-}