“Zero basis to see understand C language introduction tutorial” — (13) socket server prepared

1. Learning Objectives

1. Understand the concepts of SOCKETS in C language
2. Understand how to use C language sockets
3. The C language socket server is complete

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How to use a socket

2.1 use the socket

The following code is found on the network code, their own partial modification. (Lazy writing, ha ha ha) This content only focuses on the use of process, biased to application, too much theoretical knowledge is not emphasized. For beginners to learn the socket my personal advice is to know how to “replace” first, do a “replace” to complete the whole process to a better understanding of the problem, but for beginners, some additional extension knowledge every novice does not know, if you really need to explain the socket communication, will design a lot of network layer, So we first learn how to use socket, and then to comb these knowledge.

Because the socket practice content for some novice steps too cumbersome, in this is divided into two, one for the server, one for the client to communicate, compared to you after learning the server to view the client code will feel a flash in front of you, socket is trouble to use just ~ I wish you code yunchang Long!

Socket is based on TCP/IP. Some of you may be familiar with TCP/IP. It’s true that TCP/IP is a common word when we learn programming, it’s a protocol, and what is a protocol? Agreement means we are doing one thing, some provisions of our regulations, standards, convenient communication, communication and TCP/IP is one of the agreement, once again, we only need the socket is based on TCP/IP protocol, because in the current tutorial, talk about the agreement to one part of the reader may have a reading disorder, this is very normal. We can communicate with sockets without knowing TCP/IP, because the socket function we use is based on TCP/IP, which means we just need to know how to use sockets.

To write a C Windows socket, you need to go through several steps. First, initialize WSAStartup, create the socket, bind the socket, and bind the configuration information. If there is a connection, connect. Then use accept to receive the request. After receiving the request, you can choose to accept recV or send to send data. WSACleanup was eventually shut down.

2.2 WSAStartup Initialization

WSADATA wsaData;
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WSAStartup(MAKEWORD(1.1), &wsaData)
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WSADATA wsaData;
if (WSAStartup(MAKEWORD(1.1), &wsaData) ! =0)
{
	return 0;
}
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2.3 the socket creation

The socket is created using the Socket method. The socket accepts three parameters: the IP type, the communication type, and the last parameter that can be passed using the default type. The IP type is usually PF_INET for IPV4, the communication type is TCP, and the last parameter is 0 for the default option to match the IP type with the communication type. The code is as follows:

SOCKET slisten = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
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After the socket is created, check whether the socket is created successfully. If the socket is not created successfully, -1 is displayed:

if (slisten == - 1)
	{
		printf("socket error !");
		return 0;
	}
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2.4 the IP

struct sockaddr_in sin;
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sin.sin_family = AF_INET;
sin.sin_port = htons(8888);
sin.sin_addr.S_un.S_addr = INADDR_ANY;
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struct sockaddr_in sin;
sin.sin_family = AF_INET;
sin.sin_port = htons(8888);
sin.sin_addr.S_un.S_addr = INADDR_ANY;
if (bind(slisten, (LPSOCKADDR)&sin.sizeof(sin)) == SOCKET_ERROR)
{
	printf("bind error !");
	return 0;
}
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if (listen(slisten, 5) == SOCKET_ERROR)
{
	printf("listen error !");
	return 0;
}
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2.5 Receiving Information

Accept Accepts three parameters. The first is the socket, the second is the pointer to the sockADDR variable, and the third is the length of the received SOckADDR. The code is:

struct sockaddr_in remoteAddr;
int nAddrlen = sizeof(remoteAddr);
sClient = accept(s, (SOCKADDR *)&remoteAddr, &nAddrlen);
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After using ACCPET, the code will wait until there is a link. Then recV is used to receive the text message sent by the client. Recv takes four parameters, the first is the established communication, followed by an array, where the received data is stored, and then the cache size. The last parameter is usually set to 0. The code is:

char revData[255];
int ret = recv(sClient, revData, 255.0);
printf(revData);
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In the above RECV functions, sClient is the communication established using ACCPET, revData is the cache area for receiving information, and 255 is the length.

A data is then sent to the client, and the user responds to the client’s request for information. You can use SEND to send data to an established communication channel. The SEND function receives four parameters. The first parameter is the established communication, the second parameter is the data to be sent, the third parameter is the length of the data to be sent, and the last parameter is usually set to 0. The code is:

char * sendData = "Hello duck, I am CSDN 1_bit, ID is A757291228~\n";
send(sClient, sendData, strlen(sendData), 0);
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In the recV function above, sClient is the communication established using ACCPET, sendData is the data to be sent, 255 is the length. Finally, call the method to close the established communication:

closesocket(sClient);
closesocket(slisten);
WSACleanup();
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Since this is a one-time communication, the program will be closed after running. Here we add the stop command before the code return0:

system("pause");
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All dependency reference headers are as follows:

#include <winsock2.h>
#include <windows.h>
#include<stdio.h>
#include<stdlib.h>
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The complete code is as follows:

#include <winsock2.h>
#include <windows.h>
#include<stdio.h>
#include<stdlib.h>
 
int main(int argc, char* argv[])
{
	// Initialize WSADATA
	WSADATA wsaData;
	if (WSAStartup(MAKEWORD(2.2), &wsaData) ! =0)
	{
		return 0;
	}
 
	/ / create scoket
	SOCKET slisten = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
	if (slisten == - 1)
	{
		printf("socket error !");
		return 0;
	}
 
	// IP address of the bound port
	struct sockaddr_in sin;
	sin.sin_family = AF_INET;
	sin.sin_port = htons(8888);
	sin.sin_addr.S_un.S_addr = INADDR_ANY;
	if (bind(slisten, (LPSOCKADDR)&sin.sizeof(sin)) == SOCKET_ERROR)
	{
		printf("bind error !");
		return 0;
	}
 
	// If listening fails, return
	if (listen(slisten, 5) == SOCKET_ERROR)
	{
		printf("listen error !");
		return 0;
	}
 

	SOCKET sClient;
	struct sockaddr_in remoteAddr;
	int nAddrlen = sizeof(remoteAddr);
	sClient = accept(slisten, (SOCKADDR *)&remoteAddr, &nAddrlen);
	
	char revData[255];
	int ret = recv(sClient, revData, 255.0);
	printf(revData);
	// Send a message
	char * sendData = "Hello duck, I am CSDN 1_bit, ID is A757291228~\n";
	send(sClient, sendData, strlen(sendData), 0);
	
	closesocket(sClient);
	closesocket(slisten);
	WSACleanup();
	
	system("pause");
	return 0;
}
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If devc is used to copy code, then go to Compile -> Compile options:



Then add the following parameters to the window that appears:

conclusion