Computer network course design: design and implementation of network chat program (implemented in C language)

After aligning with the course teacher, the version written by java ended in failure. . .

Yes, my classmates came to mock me:  

       There is no other way but to write it again in C language. The code in Appendix 1 of the course design guide is blocking, that is, one server + one client, and the two send messages to each other. But the flaw is that one end can only perform one function: send or receive. That is to say, one end will block when the other end is ready to send a message, and it can only be in the state of receiving the message. Therefore, both ends cannot send messages at the same time. After the advice of friends, the thread of C language can solve this problem well.

      Server side (the main thread opens two child threads):

#include <sys/stat.h>
#include <fcntl.h>
#include <winsock2.h>
#include <windows.h>
#pragma comment(lib, "wsock32.lib")
#include <errno.h>
#include<stdlib.h>
#include<string.h>
#include <sys/types.h>
#include<ws2tcpip.h>
#include <stdio.h>
#include <unistd.h>
#include <process.h>
#define SERVER_PORT 6666

//全局变量
int client;	int iDataNum;
char buffer[200]; //存储 发送和接收的信息

void rece(){//形参void * 不可省略，否则编译出错
        while(1){
			buffer[0] = '\0';
			iDataNum = recv(client, buffer, 1024, 0);
			if(iDataNum < 0)
	//			perror("recv null");
				continue;
            else{
                buffer[iDataNum] = '\0';
            	if(strcmp(buffer, "quit") == 0)
                    break;
			printf("收到来自客户端的消息: %s\n", buffer);
            }
        Sleep(3000);
    }
    printf("后台线程结束\n\n");
    _endthread();
}

void sendm(){//形参void * 不可省略，否则编译出错
    while(1){
        scanf("%s", buffer);
        send(client, buffer, strlen(buffer), 0); //服务端也向客户端发送消息
     //    if(strcmp(buffer, "quit") == 0) break;输入quit停止服务端程序
     }
}

int main()
{
	//调用socket函数返回的文件描述符
	int serverSocket;

	//声明两个套接字sockaddr_in结构体变量，分别表示客户端和服务器
	struct sockaddr_in server_addr;
	struct sockaddr_in clientAddr;

	int addr_len = sizeof(clientAddr);

	//必须先初始化
	WSADATA wsaData;
	WSAStartup(MAKEWORD(2,2),&wsaData);
	if(LOBYTE(wsaData.wVersion) != 2 || HIBYTE(wsaData.wVersion) !=2){
	    printf("require version fail!");
	    return -1;
	}

	//socket函数，失败返回-1
	//int socket(int domain, int type, int protocol);
	//第一个参数表示使用的地址类型，一般都是ipv4，AF_INET
	//第二个参数表示套接字类型：tcp：面向连接的稳定数据传输SOCK_STREAM
	//第三个参数设置为0
	//建立socket
	if((serverSocket = socket(AF_INET,SOCK_STREAM,IPPROTO_TCP)) < 0)
	{
		perror("socket");
		return 1;
	}

	//初始化 server_addr
	memset(&server_addr,0, sizeof(server_addr));

	//初始化服务器端的套接字，并用htons和htonl将端口和地址转成网络字节序
	server_addr.sin_family = AF_INET;
	server_addr.sin_port = htons(SERVER_PORT);

	//ip可是是本服务器的ip，也可以用宏INADDR_ANY代替，代表0.0.0.0，表明所有地址
	server_addr.sin_addr.s_addr = htonl(INADDR_ANY);

	//对于bind，accept之类的函数，里面套接字参数都是需要强制转换成(struct sockaddr *)
	//bind三个参数：服务器端的套接字的文件描述符，
	if(bind(serverSocket, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0)
	{
		perror("connect");
		return 1;
	}

	//设置服务器上的socket为监听状态,5为最大的客户端线程数
	if(listen(serverSocket, 5) < 0)
	{
		perror("listen");
		return 1;
	}

	//循环 接收消息、发送消息
	while(1)
	{
		printf("监听端口: %d\n", SERVER_PORT);

		//调用accept函数后，会进入阻塞状态
		//accept返回一个套接字的文件描述符，这样服务器端便有两个套接字的文件描述符，
		//serverSocket和client。
		//serverSocket仍然继续在监听状态，client则负责接收和发送数据
		//clientAddr是一个传出参数，accept返回时，传出客户端的地址和端口号
		//addr_len是一个传入-传出参数，传入的是调用者提供的缓冲区的clientAddr的长度，以避免缓冲区溢出。
		//传出的是客户端地址结构体的实际长度。
		//出错返回-1


		client = accept(serverSocket, (struct sockaddr*)&clientAddr, (socklen_t*)&addr_len);

		if(client < 0)
		{
			perror("accept");
			continue;
		}

		printf("等待消息...\n");

		//inet_ntoa ip地址转换函数，将网络字节序IP转换为点分十进制IP
		//表达式：char *inet_ntoa (struct in_addr);
		printf("IP is %s\n", inet_ntoa(clientAddr.sin_addr)); //把来访问的客户端的IP地址打出来
		printf("Port is %d\n", htons(clientAddr.sin_port));

            _beginthread(rece,0,NULL);//开启一个接受消息线程
            _beginthread(sendm,0,NULL);//开启一个发送消息线程
		}
	close(serverSocket);
	return 0;
}

Client (the main thread only opens one thread for receiving messages, and the main thread is responsible for sending messages to the server):

#include <sys/stat.h>
#include <fcntl.h>
#include <winsock2.h>
#include <windows.h>
#pragma comment(lib, "wsock32.lib")
#include <errno.h>
#include<stdlib.h>
#include<string.h>
#include <sys/types.h>
#include<ws2tcpip.h>
#include <stdio.h>
#include <unistd.h>
#include <process.h>
#define SERVER_PORT 6666

char recvbuf[200]; //存储 接收到的信息
int iDataNum;
//客户端只需要一个套接字文件描述符，用于和服务器通信
int serverSocket;

void rece(){//形参void * 不可省略，否则编译出错
        while(1){
		recvbuf[0] = '\0';
		iDataNum = recv(serverSocket,recvbuf,200,0); //接收服务端发来的消息,返回信息长度
        recvbuf[iDataNum] = '\0';
		if(iDataNum>0)
        {
             printf("收到来自服务器的消息: %s\n",recvbuf);
        }
        Sleep(3000);//线程休眠3s，表示每隔3s查看一次是否有来自客户端的消息
    }
    printf("后台线程结束\n\n");
    _endthread();
}

int main()
{
	//描述服务器的socket
	struct sockaddr_in serverAddr;

	char sendbuf[200]; //存储 发送的信息

	//下面代码初始化
	WSADATA wsaData;
	WSAStartup(MAKEWORD(2,2),&wsaData);
	if(LOBYTE(wsaData.wVersion) != 2 || HIBYTE(wsaData.wVersion) !=2){
	    printf("require version fail!");
	    return -1;
	}

	if((serverSocket = socket(AF_INET,SOCK_STREAM,IPPROTO_TCP)) < 0)
	{
		perror("socket");
		return 1;
	}

	//描述服务端的serverAddr,其中SERVER_PORT为6666
	serverAddr.sin_family = AF_INET;
	serverAddr.sin_port = htons(SERVER_PORT);

	//指定服务器端的ip，本地测试：127.0.0.1
	//inet_addr()函数，将点分十进制IP转换成网络字节序IP
	serverAddr.sin_addr.s_addr = inet_addr("127.0.0.1");

	if(connect(serverSocket, (struct sockaddr *)&serverAddr, sizeof(serverAddr)) < 0)
	{
		perror("connect");
		return 1;
	}

	printf("连接到主机...\n");
    _beginthread(rece,0,NULL);//开启一个接收消息线程
	while(1)
	{
		scanf("%s", sendbuf);
		send(serverSocket, sendbuf, strlen(sendbuf), 0); //向服务端发送消息
		if(strcmp(sendbuf, "quit") == 0) break;.
	}
	close(serverSocket);
	return 0;
}

I wrote the code after adding the thread function on the basis of another article, and attach the blog post link: https://www.cnblogs.com/fisherss/p/12085123.html

Effect picture (only text prompts for receiving messages, no text prompts for sending messages):

flow chart: