C Socket Programming Video Tutorial113

## Introduction
Socket programming is a fundamental concept in computer networking that allows applications to communicate over a network. In this video tutorial, we will explore the basics of socket programming using the C language. We will cover the different types of sockets, how to create and use sockets, and how to send and receive data over a network.
## Socket Types
There are two main types of sockets in C:
* Stream sockets: Stream sockets provide a reliable, ordered, and bidirectional channel for data transmission. They are typically used for applications that need to maintain a persistent connection, such as web servers and email clients.
* Datagram sockets: Datagram sockets provide an unreliable, unordered, and unidirectional channel for data transmission. They are typically used for applications that do not require a persistent connection, such as UDP-based games and messaging systems.
## Creating Sockets
To create a socket, we use the `socket` function. The `socket` function takes three arguments:
* socket domain: The socket domain specifies the addressing scheme to be used for the socket. Common socket domains include AF_INET (IPv4) and AF_INET6 (IPv6).
* socket type: The socket type specifies the type of socket to be created. Common socket types include SOCK_STREAM (stream sockets) and SOCK_DGRAM (datagram sockets).
* protocol: The protocol specifies the specific protocol to be used for the socket. Common protocols include TCP (for stream sockets) and UDP (for datagram sockets).
For example, to create a TCP stream socket, we would use the following code:
```c
int sockfd = socket(AF_INET, SOCK_STREAM, 0);
```
## Binding Sockets
Before we can use a socket, we need to bind it to a specific IP address and port. The `bind` function is used to bind a socket to an address. The `bind` function takes two arguments:
* sockfd: The file descriptor of the socket to be bound.
* sockaddr: The address structure to be bound to the socket.
The sockaddr structure contains the IP address and port number of the socket. For example, to bind a socket to the IP address 127.0.0.1 and port 8080, we would use the following code:
```c
struct sockaddr_in addr;
addr.sin_family = AF_INET;
addr.sin_port = htons(8080);
addr.sin_addr.s_addr = inet_addr("127.0.0.1");
bind(sockfd, (struct sockaddr*)&addr, sizeof(addr));
```
## Connecting Sockets
If we are creating a client socket, we need to connect the socket to a server socket. The `connect` function is used to connect a socket to a remote address. The `connect` function takes two arguments:
* sockfd: The file descriptor of the socket to be connected.
* sockaddr: The address structure of the remote socket to be connected to.
For example, to connect a client socket to a server socket at the IP address 127.0.0.1 and port 8080, we would use the following code:
```c
struct sockaddr_in addr;
addr.sin_family = AF_INET;
addr.sin_port = htons(8080);
addr.sin_addr.s_addr = inet_addr("127.0.0.1");
connect(sockfd, (struct sockaddr*)&addr, sizeof(addr));
```
## Sending and Receiving Data
Once we have established a connection between two sockets, we can send and receive data using the `send` and `recv` functions, respectively. The `send` function takes three arguments:
* sockfd: The file descriptor of the socket to be sent to.
* buf: The buffer containing the data to be sent.
* len: The length of the data to be sent.
The `recv` function takes three arguments:
* sockfd: The file descriptor of the socket to be received from.
* buf: The buffer to receive the data into.
* len: The length of the buffer.
For example, to send data from a client socket to a server socket, we would use the following code:
```c
char *buf = "Hello, world!";
send(sockfd, buf, strlen(buf), 0);
```
To receive data from a server socket on a client socket, we would use the following code:
```c
char buf[1024];
recv(sockfd, buf, sizeof(buf), 0);
```
## Closing Sockets
When we are finished using a socket, we should close it using the `close` function. The `close` function takes one argument:
* sockfd: The file descriptor of the socket to be closed.
For example, to close a socket, we would use the following code:
```c
close(sockfd);
```

2024-12-03

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