--Socket chapter of CS network data exchange

1. View man socket terminal input socket of related content
2. Create a server socket

/*
第一个参数domain（网络类型）：PF_INET ipv4/PF_INET6 ipv6
第二个参数type（socket类型）：SOCK_STREAM面向连接的——TCP协议/SOCK_DGRAM无连接的——UDP协议
第三个参数protocol：
*/
int serverSocket = socket(PF_INET, SOCK_STREAM, 0);
if (serverSocket == -1) {
    NSLog(@"创建失败");
}else{
    NSLog(@"创建成功");
}

2. Bind port number

int bind(SOCKET sock, const struct sockaddr *addr, int addrlen);

The first argument: socket file descriptor has been created,
The second parameter: the incoming address structure. Due to compatibility with older systems, function declarations type struct sockaddr *, but we generally use sockaddr_in, which is easier to use.

//创建sockaddr_in结构体变量
struct sockaddr_in addr;
addr.sin_family = AF_INET;//使用ipv4地址
addr.sin_addr.s_addr = htonl(INADDR_ANY);//绑定ip地址为任意
addr.sin_port = htons(1234);//端口号

int result = bind(serverSocket, (const struct sockaddr *)&addr, sizeof(addr));
if (result == -1) {
    NSLog(@"绑定出错");
}else{
    NSLog(@"绑定成功");
}

3. Start listening

int listen(SOCKET sock, int backlog);

sock need to enter the monitoring state for the socket, backlog for the maximum length of the request queue.

result = listen(serverSocket, 5);
if (result == -1) {
    NSLog(@"监听失败");
}else{
    NSLog(@"开始监听");
}

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4. Accept

SOCKET accept(SOCKET sock, struct sockaddr *addr, int *addrlen);

It is a server-side socket sock, sockaddr_in addr of structure variables, parameters addr addrlen the length, by the sizeof () is obtained.

//保存客户端的信息
struct sockaddr c_addr;
socklen_t len;
//保存接收的数据 缓存区
char *buff[1024];
while (1) {
    int newSocket = accept(serverSocket, (struct sockaddr *)&c_addr, &len);
    if (newSocket == -1) {
        NSLog(@"接收数据失败");
    }else{
        NSLog(@"开始聊天了");
        //接收数据
        size_t length = recv(newSocket, buff, 1024, 0);
        NSLog(@"接收了%zu字节：%s",length ,buff);
        
        //发送数据
        char *msg = "hello";
        length = send(newSocket, msg, strlen(msg), 0);
        NSLog(@"成功发送给客户端%zu字节",length);
    }
}

5. The client creates socket

Import header file

#import <sys/socket.h>
#import<netinet/in.h>
#import <arpa/inet.h>
#import <sys/types.h>

	int clientSocket = socket(PF_INET, SOCK_STREAM, 0);
    if (clientSocket == -1) {
        NSLog(@"创建失败");
    }else{
        NSLog(@"创建成功");
    }

6. initiate a connection

int connect(SOCKET sock, const struct sockaddr *serv_addr, int addrlen);

struct sockaddr_in addr;
addr.sin_family = AF_INET;//ipv4 
addr.sin_addr.s_addr = inet_addr("127.0.0.1");//绑定具体的ip地址
addr.sin_port = htons(1234);//绑定端口号

int result = connect(clientSocket, (const struct sockaddr *)&addr, sizeof(addr));
if (result == -1) {
    NSLog(@"连接出错");
}else{
    NSLog(@"连接成功");
}

7. Data transmission

//发送数据
char *msg = "hello world";
ssize_t len = send(clientSocket, msg, strlen(msg), 0);
NSLog(@"成功发送 %zd 字节",len);

The receiving data

char buff[1024];
len = recv(clientSocket, buff, 1024, 0);
NSLog(@"成功接收%zd字节",len,buff);

9. results
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--Socket chapter of CS network data exchange

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