Basic example af unix tcp server and client

AF_UNIX TCP

• In this program, you are going to learn

• How to create a Socket ?

• How to bind a socket ?

• How to listen a socket ?

• How to connect a socket ?

• How to accept a socket ?

• How to send a data ?

• How to recv a data ?

• How to use socket APIs ?

  • socket

  • bind

  • listen

  • connect

  • accept

  • send

  • recv

Topics in this section,

• program 1: af unix tcp single server and single client : single data transfer

• program 2: af unix tcp single server and single client : multiple data transfer

program 1 : af unix tcp single server and single client : single data transfer

Topics in this section,

• AF_UNIX TCP SOCKET FAQs

• Program1 : Step 1: Sequence Diagram for SERVER.c

• Program1 : Step 2: Program for Server.c

• Program1 : Step 3: Compile and Execute Server.c

• Program1 : Step 4: Sequence Diagram for CLIENT.c

• Program1 : Step 5: Program for Client.c

• Program1 : Step 6: Compile and Execute Client.c

• Summary

program 2 : af unix tcp single server and single client : multiple data transfer

Topics in this section,

• AF_UNIX TCP SOCKET FAQs

• Program2 : Step 1: Sequence Diagram for SERVER.c

• Program2 : Step 2: Program for Server.c

• Program2 : Step 3: Compile and Execute Server.c

• Program2 : Step 4: Sequence Diagram for CLIENT.c

• Program2 : Step 5: Program for Client.c

• Program2 : Step 6: Compile and Execute Client.c

• Summary

AF_UNIX TCP SOCKET : FAQs

Let us answer few basic questions in this socket

What does AF_UNIX represent in the socket call?

See Answer

AF_UNIX represents the Unix domain socket family. It is used for communication between processes on the same machine, using file system paths as addresses.

Why use SOCK_STREAM as the socket type?

See Answer

SOCK_STREAM indicates a stream-oriented socket, providing a reliable, connection-oriented communication channel.

What does the third parameter (0) indicate in socket(AF_UNIX, SOCK_STREAM, 0)?

See Answer

Default protocol selected by the system.

How can I set up a server and client using AF_UNIX sockets?

See Answer

To set up a server and client,

create a socket using socket(AF_UNIX, SOCK_STREAM, 0),

bind the server to an address,

isten for incoming connections, and establish connections from clients.

Communication occurs through read and write operations on the established connections.

How should errors in the socket call be handled?

See Answer

Check the return value, handle errors using appropriate mechanisms.

What is the role of the file system path in AF_UNIX sockets?

See Answer

The file system path serves as the address for Unix domain sockets. It enables processes to locate and connect to the socket. he path is set in the sun_path field of the struct sockaddr_un structure.

What is the role of the file system path in AF_UNIX sockets?

See Answer

Address.

Why might bind() or listen() fail in socket programming?

See Answer

bind() might fail if the specified address is already in use, or if the process lacks the necessary permissions. listen() might fail if the socket is not bound, or the operating system limit for pending connections is reached.

How should you handle errors when using accept() in socket programming?

See Answer

Check the return value and handle errors appropriately

Why is it important to check the return value of send() and recv() in socket programming?

See Answer

It detects issues such as network errors or closed connections.

Program1 : Step 1: Sequence Diagram for SERVER.c

Program1 : Step 2: Program for Server.c

• There are many functions used in socket. We can classify those functions based on functionalities.

  • Create Socket

  • Bind Socket

  • Listen Socket

  • Accept Socket

  • Recv data_packet

  • Send data_packet

  • Close socket

• socket() is used to create a new socket. For example,

server_socket =  socket(AF_UNIX, SOCK_STREAM, 0);

• bind() is used to associate the socket with a specific address and port. For example,

ret = bind(server_socket, (struct sockaddr*)&server_addr, sizeof(server_addr));

• listen() is used to set up a socket to accept incoming connections. For example,

ret = listen(server_socket, 5);

• accept() is used in network programming on the server side to accept a connection request from a client. For example,

client_socket = accept(server_socket, (struct sockaddr*)&client_addr, &addr_size);

• recv is used in network programming to receive data from a connected socket. For example,

ret = recv(client_socket, buffer, sizeof(buffer), 0);

• send is used in network programming to send data over a connected socket. For example,

ret = send(client_socket, buffer, strlen(buffer), 0);

• close is used to close the socket To free up system resources associated with the socket. For example,

(void)close(client_socket);

• See the full program below,

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/un.h>

#define SOCKET_PATH "/tmp/my_unix_socket"
#define BUFFER_SIZE 1024

int main(void) 
{
  int server_socket;
  int client_socket;
  int ret;
  struct sockaddr_un 
  server_addr, 
  client_addr;
  socklen_t addr_size = sizeof(
  client_addr);
  char buffer[BUFFER_SIZE] 
  = "Hello from server!";

  server_addr.sun_family = AF_UNIX;
  strncpy(server_addr.sun_path, 
  SOCKET_PATH, 
  sizeof(server_addr.sun_path) - 1);
  unlink(SOCKET_PATH);

  server_socket = socket(AF_UNIX, 
                  SOCK_STREAM, 
                  0);

  if (server_socket < 0) {
    perror("Socket failed");
    return -1;
  }

  ret = bind(server_socket, 
  (struct sockaddr *)&server_addr, 
  sizeof(server_addr));

  if (ret < 0) {
    perror("Bind failed");
    (void)close(server_socket);
    return -2;
  }

  ret = listen(server_socket, 5);

  if (ret < 0) {
    perror("Listen failed");
    (void)close(server_socket);
    return -3;
  }

  client_socket = accept(
  server_socket, 
  (struct sockaddr *)&client_addr, 
  &addr_size);

  if (client_socket < 0) {
    perror("Accept failed");
    (void)close(server_socket);
    return -4;
  }

  ret = recv(client_socket, 
  buffer,
  sizeof(buffer), 0);

  if (ret < 0) {
    perror("recv");
    (void)close(server_socket);
    (void)close(client_socket);
    return -5;
  }

  buffer[ret] = '\0';
  printf("Received: %s\n",
  buffer);

  memset(buffer, 0, 
  sizeof(buffer));

  strncpy(buffer, "Hello CLient\n", 
  strlen("Hello CLient\n") + 1);
  buffer[strlen("Hello CLient\n") 
  + 1] = '\0';

  ret = send(client_socket, buffer, 
  strlen(buffer), 0);

  if (ret < 0) {
    perror("send");
    (void)close(client_socket);
    return -6;
  }

  (void)close(client_socket);
  (void)close(server_socket);

  return 0;
}

Program1 : Step 3: Compile and Execute Server.c

$ gcc -o server server.c

$ sudo ./server

Received: Hello Server!

Program1 : Step 4: Sequence Diagram for CLIENT.c

Program1 : Step 5: Program for Client.c

• There are many functions used in socket. We can classify those functions based on functionalities.

  • Create Socket

  • Connect Socket

  • Send data_packet

  • Recv data_packet

  • Close socket

• socket is used to create a new socket. For example,

client_socket = socket(AF_UNIX, SOCK_STREAM, 0);

• connect is used in network programming to establish a connection from a client to a server. For example,

ret = connect(client_socket, (struct sockaddr*)&server_addr, sizeof(server_addr));

• send is used in network programming to send data over a connected socket. For example,

ret = send(client_socket, buffer, strlen(buffer), 0);

• recv is used in network programming to receive data from a connected socket. For example,

ret = recv(client_socket, buffer, sizeof(buffer), 0);

• close is used to close the socket To free up system resources associated with the socket. For example,

(void)close(client_socket);

• See the full program below,

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/un.h>

#define SOCKET_PATH "/tmp/my_unix_socket"
#define BUFFER_SIZE 1024

int main(void) 
{
  int client_socket;
  int ret;
  struct sockaddr_un server_addr;
  char buffer[BUFFER_SIZE] 
  = "Hello Server!";

  server_addr.sun_family = AF_UNIX;
  strncpy(server_addr.sun_path, 
  SOCKET_PATH, 
  sizeof(server_addr.sun_path) - 1);

  client_socket = socket(AF_UNIX, 
  SOCK_STREAM, 0);

  if (client_socket < 0) {
    perror("Socket failed");
    return -1;
  }

  ret = connect(client_socket, 
  (struct sockaddr *)&server_addr, 
  sizeof(server_addr));

  if (ret < 0) {
    perror("Connection failed");
    (void)close(client_socket);
    return -2;
  }

  ret = send(client_socket, 
  buffer,
  strlen(buffer), 0);

  if (ret < 0) {
    perror("send");
    (void)close(client_socket);
    return -3;
  }

  memset(buffer, 0, 
  sizeof(buffer));

  ret = recv(client_socket, 
  buffer, 
  sizeof(buffer), 0);

  if (ret < 0) {
    perror("recv");
    (void)close(client_socket);
    return -4;
  }

  printf("Received: %s", 
  buffer);  

  (void)close(client_socket);

  return 0;
}

Program1 : Step 6: Compile and Execute Client.c

$ gcc -o client client.c

$ sudo ./client

Received: Hello CLient

Program2 : Step 1: Sequence Diagram for SERVER.c

Program2 : Step 2: Program for Server.c

• There are many functions used in socket. We can classify those functions based on functionalities.

  • Create Socket

  • Bind Socket

  • Listen Socket

  • Accept Socket

  • Recv data_packet

  • Send data_packet

  • Close socket

• socket() is used to create a new socket. For example,

server_socket = socket(AF_UNIX, SOCK_STREAM, 0);

• bind() is used to associate the socket with a specific address and port. For example,

ret = bind(server_socket, (struct sockaddr*)&server_addr, sizeof(server_addr));

• listen() is used to set up a socket to accept incoming connections. For example,

ret = listen(server_socket, 5);

• accept() is used in network programming on the server side to accept a connection request from a client. For example,

client_socket = accept(server_socket, (struct sockaddr*)&client_addr, &addr_size);

• send is used in network programming to send data over a connected socket. For example,

ret = send(client_socket, buffer, strlen(buffer), 0);

• recv is used in network programming to receive data from a connected socket. For example,

ret = recv(client_socket, buffer, sizeof(buffer), 0);

• close is used to close the socket To free up system resources associated with the socket. For example,

(void)close(client_socket);

• See the full program below,

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/un.h>

#define SOCKET_PATH "/tmp/my_unix_socket"
#define BUFFER_SIZE 1024
#define NUM_MESSAGES 10

int main(void) 
{
  int server_socket;
  int client_socket;
  int ret, i;
  struct sockaddr_un 
  server_addr, 
  client_addr;
  socklen_t addr_size = sizeof(
  client_addr);
  char buffer[BUFFER_SIZE]; 

  server_addr.sun_family = AF_UNIX;
  strncpy(server_addr.sun_path, 
  SOCKET_PATH, 
  sizeof(server_addr.sun_path) - 1);
  unlink(SOCKET_PATH);

  server_socket = socket(AF_UNIX, 
                  SOCK_STREAM, 0);

  if (server_socket < 0) {
    perror("Socket failed");
    return -1;
  }

  ret = bind(server_socket, 
  (struct sockaddr *)&server_addr, 
  sizeof(server_addr));

  if (ret < 0) {
    perror("Bind failed");
    (void)close(server_socket);
    return -2;
  }

  ret = listen(server_socket, 5);

  if (ret < 0) {
    perror("Listen failed");
    (void)close(server_socket);
    return -3;
  }

  client_socket = accept(
  server_socket, 
  (struct sockaddr *)&client_addr, 
  &addr_size);

  if (client_socket < 0) {
    perror("Accept failed");
    (void)close(server_socket);
    return -4;
  }

  i = 0;
  while (i < NUM_MESSAGES) {   
   memset(buffer, 0, 
   sizeof(buffer));
   ret = recv(client_socket, 
   buffer,
   sizeof(buffer), 0);

   if (ret < 0) {
      perror("recv");
      break;
    }

    printf("Received: %s\n", 
    buffer);

    memset(buffer, 0, 
    sizeof(buffer));

    strncpy(buffer, "Hello CLient\n", 
    strlen("Hello CLient\n") + 1);
    buffer[strlen("Hello CLient\n") 
    + 1] = '\0';

    ret = send(client_socket,
    buffer, 
    strlen(buffer), 0);

    if (ret < 0) {
      perror("send");
      break;
   }
   ++i;
  }

  (void)close(server_socket);
  (void)close(client_socket);

  return 0;
}

Program2 : Step 3: Compile and Execute Server.c

$ gcc -o server server.c

$ sudo ./server

Received: Hello Server!
Received: Hello Server!
Received: Hello Server!
Received: Hello Server!
Received: Hello Server!
Received: Hello Server!
Received: Hello Server!
Received: Hello Server!
Received: Hello Server!
Received: Hello Server!

Program2 : Step 4: Sequence Diagram for CLIENT.c

Program2 : Step 5: Program for Client.c

• There are many functions used in socket. We can classify those functions based on functionalities.

  • Create Socket

  • Connect Socket

  • Send data_packet

  • Recv data_packet

  • Close socket

• socket is used to create a new socket. For example,

client_socket = socket(AF_UNIX, SOCK_STREAM, 0);

• connect is used in network programming to establish a connection from a client to a server. For example,

ret = connect(client_socket, (struct sockaddr*)&server_addr, sizeof(server_addr));

• send is used in network programming to send data over a connected socket. For example,

ret = send(client_socket, buffer, strlen(buffer), 0);

• recv is used in network programming to receive data from a connected socket. For example,

ret = recv(client_socket, buffer, sizeof(buffer), 0);

• close is used to close the socket To free up system resources associated with the socket. For example,

(void)close(client_socket);

• See the full program below,

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/un.h>

#define SOCKET_PATH "/tmp/my_unix_socket"
#define BUFFER_SIZE 1024
#define NUM_MESSAGES 10

int main(void) 
{
  int client_socket;
  int ret, i;
  struct sockaddr_un 
  server_addr;
  char buffer[BUFFER_SIZE]; 

  server_addr.sun_family = AF_UNIX;
  strncpy(server_addr.sun_path, 
  SOCKET_PATH, 
  sizeof(server_addr.sun_path) - 1);

  client_socket = socket(AF_UNIX, 
                  SOCK_STREAM, 0);

  if (client_socket < 0) {
    perror("Socket failed");
    return -1;
  }

  ret = connect(client_socket, 
  (struct sockaddr *)&server_addr, 
  sizeof(server_addr));

  if (ret < 0) {
    perror("Connection failed");
    (void)close(client_socket);
    return -2;
  }

  i = 0;
  while (i < NUM_MESSAGES) {
    ret = send(client_socket, 
    "Hello Server!",
    strlen("Hello Server!"), 0);

    if (ret < 0) {
      perror("send");
      break;
    }

    memset(buffer, 0, 
    sizeof(buffer));

    ret = recv(client_socket, buffer, 
    sizeof(buffer), 0);

    if (ret < 0) {
      perror("recv");
      break;
    }

    printf("Received: %s", 
    buffer);
    ++i;
  }

  (void)close(client_socket);

  return 0;
}

Program2 : Step 6: Compile and Execute Client.c

$ gcc -o client client.c

$ sudo ./client

Received: Hello CLient
Received: Hello CLient
Received: Hello CLient
Received: Hello CLient
Received: Hello CLient
Received: Hello CLient
Received: Hello CLient
Received: Hello CLient
Received: Hello CLient
Received: Hello CLient

Summary

Socket API	Learning
socket	Create a new socket
bind	Associate the socket with a specific address and port
listen	Set up a socket to accept incoming connections.
connect	Establish a connection from a client to a server.
accept	Server side to accept a connection request from a client.
recv	Receive data from a connected socket.
send	Send data over a connected socket.

See Also

• Previous topic

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• Current topic

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• Next topic

  • af unix tcp server client program with Select system call

• Other sockets

  • af_unix_udp

  • ipv4_raw_af_inet_icmp

  • ipv4_raw_af_inet_raw

  • ipv4_raw_af_inet_tcp

  • ipv4_raw_af_inet_udp

  • ipv6_af_inet6_tcp

  • ipv6_af_inet6_udp

  • //TODO ipv6_raw_af_inet6_icmp

  • //TODO ipv6_raw_af_inet6_tcp

  • //TODO ipv6_raw_af_inet6_udp

  • // TODO ipv6_raw_af_inet6_raw

  • raw_af_packet_raw_htons_ETH_P_ALL

  • raw_af_packet_tcp_htons_ETH_P_ALL

  • raw_af_packet_udp_htons_ETH_P_ALL

• Other IPCs

  • Message_queues

  • NamedPipes

  • Netlink

  • Shared_Memory

  • Shared_Memory_2_FDS

  • SocketPair

  • Timerfd