9. "Ten Thousand Miles" Raspberry Pi Car - Socket Learning (TCP Two-Machine Communication)

lb8820265 · 2021-11-29 01:02 上传

9. "Ten Thousand Miles" Raspberry Pi Car - Socket Learning (TCP Two-Machine Communication) [Copy link]

We have previously introduced the communication between sockets on the local computer under Windows and Linux. This is meaningless because it requires two computers to communicate with each other and to send and receive messages continuously.

Next, based on the previous code, we will make a two-machine communication, with Linux (Raspberry Pi) as the server and Windows as the client, connected to the same router.

Coding

socket_TCP_win_client_2.cpp under windows

#include <stdio.h>
#include <WinSock2.h>
#pragma comment(lib, "ws2_32.lib") //加载 ws2_32.dll
#define BUF_SIZE 100
int main(){
//初始化DLL
WSADATA wsaData;
WSAStartup(MAKEWORD(2, 2), &wsaData);
//创建套接字
SOCKET sock = socket(PF_INET, SOCK_DGRAM, 0);
//服务器地址信息
sockaddr_in servAddr;
memset(&servAddr, 0, sizeof(servAddr)); //每个字节都用0填充
servAddr.sin_family = PF_INET;
servAddr.sin_addr.s_addr = inet_addr("127.0.0.1");
servAddr.sin_port = htons(1234);
//不断获取用户输入并发送给服务器，然后接受服务器数据
sockaddr fromAddr;
int addrLen = sizeof(fromAddr);
while(1){
char buffer[BUF_SIZE] = {0};
printf("Input a string: ");
gets(buffer);
sendto(sock, buffer, strlen(buffer), 0, (struct sockaddr*)&servAddr, sizeof(servAddr));
int strLen = recvfrom(sock, buffer, BUF_SIZE, 0, &fromAddr, &addrLen);
buffer[strLen] = 0;
printf("Message form server: %s\n", buffer);
}
closesocket(sock);
WSACleanup();
return 0;
}

socket_TCP_linux_client_2.cpp under Linux

#define BUF_SIZE 100
int main(){
//创建套接字
int serv_sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
//将套接字和IP、端口绑定
struct sockaddr_in serv_addr;
memset(&serv_addr, 0, sizeof(serv_addr)); //每个字节都用0填充
serv_addr.sin_family = AF_INET; //使用IPv4地址
serv_addr.sin_addr.s_addr = htonl(INADDR_ANY); //具体的IP地址
serv_addr.sin_port = htons(1234); //端口
bind(serv_sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr));
//进入监听状态，等待用户发起请求
listen(serv_sock, 20);
//接收客户端请求
struct sockaddr_in clnt_addr;
socklen_t clnt_addr_size = sizeof(clnt_addr);
char buffer[BUF_SIZE] = {0}; //缓冲区
while(1){
memset(&buffer, 0, sizeof(buffer)); //每个字节都用0填充
int clnt_sock = accept(serv_sock, (struct sockaddr*)&clnt_addr, &clnt_addr_size);
int strLen = recv(clnt_sock, buffer, BUF_SIZE, 0); //接收客户端发来的数据
//向客户端发送数据
printf("recieve:%s",buffer);
write(clnt_sock, buffer, strLen);
//关闭套接字
close(clnt_sock);
memset(buffer, 0, BUF_SIZE); //重置缓冲区
}
close(serv_sock);
return 0;
}

Key Points

The most important point of communication between two machines is that the client needs to know the IP address of the server, and the server registers the socket with the local address. The following code sets the socket to the local IP address.

servAddr .sin_addr.S_un.S_addr =htonl(INADDR_ANY);

The address setting code in the client is

servAddr .sin_addr.S_un.S_addr = inet_addr("192.168.31.159");

The IP address in the code is the IP address of the Raspberry Pi, which can be viewed by entering the ifconfig command.

How to run

Compile and run the server code in Linux first;
Compile and run the client code in Windows.
Enter the data to be transmitted in the Windows terminal and press Enter. After the Raspberry Pi server receives the data, it will send it to the Windows client.

Operation effect

[attach]575403[/attach ]

As can be seen from the while loop, completing a transmission process is quite cumbersome, requiring frequent connection establishment, disconnection, and multiple handshakes. Is there a more convenient transmission method?

Source code

GitHub:

Linux server

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http://github.com/wanli-car/Examples/blob/master/C++/Socket/Linux/socket_TCP_linux_server_2.cpp

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Windows client:

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Gitee:

Linux server:

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Windows client: