Socket Introduction (Master Socket family)

0. nc-lk Port number : always listen for data on this port on the local computer .         1. Import three header files     { #import <sys/socket.h> #import <netinet/in.h> #import <arpa/inet.h>     }     2. Socket writing steps     { 1. Create client socket socket (< #int #>, < #int #>, < #int #>); c8> 2. Create a server Socket struct sockaddr_in serveraddr ESS; 3. Connect to the server (Socket programming) Connect (< #int #>, < #const struct S Ockaddr *#>, < #socklen_t #>); 4. send data to server send (< #int #>, < #const void *#>, < #size_t #> < #int #>) 5. receive the data returned by the server recv (< #int #>, < #void *#>, < #size_t #> , < #int #>) 6. closing the Socket Close (socketnumber)     }         /* Create a client Socket. three parameters: domain: Network address types Type: Port type Protocal: Transport Protocol      Domain : the protocol field specifies the socket host address type . Network Layer Protocol Af_inet/ipv4 Protocol ; Af_inet_6/ipv6 Protocol      Type : Specifies the Socket Port type . Specify the Transport layer protocol type (TCP/UDP), Sock_stream (tcp/ stream ), Sock_dgram (udp/ message header )      protocal: Specify transport protocol : Common Protocol : Ipproto_tcp,ipproto_udp and so on, respectively, corresponding to TCP Transport protocol,UDP Transmission protocol .      The last parameter , 0, automatically selects the protocol corresponding to the second parameter according to the second parameter .      return value: If > 0 indicates success.      */     // 0. Create client Socket. int Socketnumber = socket (af_inet, sock_stream, 0);     if (Socketnumber > 0) { NSLog (@ "Socket creation succeeded :%d", socketnumber); }else{ NSLog (@ "Socket creation failed ");     };         /* Connect to the server. three parameters:      1. client socket. 2. the receiver's socket parameters . 3. Data length .      return value: 0 indicates success, other: error code .      */         // 1. Server Socket struct sockaddr_in serveraddress; //IPV4 protocol. serveraddress.sin_family = af_inet; //Receiver (server) IP address. serverAddress.sin_addr.s_addr = inet_addr ("127.0.0.1"); //port number. serveraddress.sin_port = htons (56789);         // 2. Connect to server   // /serveraddress data length . socklen_t length = sizeof(serveraddress); //Connect to the server . //In the C language, the length of the struct is specified when passing the structure body //& takes the starting position of the data, only passing the length of one data, To ensure that the complete structure data is obtained . //Return value: 0 success, others are failures. int connection = connect (socketnumber, const struct SOCKADDR *) &serveraddress,length);     if (!connection) { NSLog (@ " connection succeeded %d", connection); }else{ NSLog (@ " Connection failed ");     }         /* send a message to the server parameters : 1> client Socket. 2> send content address . 3> send content length . 4> Send way identification , generally 0.           */     // 3. send a message to the server     // Send message content nsstring *msg = @ "Hello socket!";     msg.length: represents the length of the OC string . Msg. Utf8string: Converts an OC string to an ASCII code of UTF8 , a Chinese character needs to occupy 3 the length of a byte . strlen: calculates The length of all ASCII codes.     // Send message ssize_t result = Send (Socketnumber, MSG. Utf8string, strlen (Msg. utf8string), 0);     NSLog (@ "result =%ld", result);         /* receiving the message returned by the server parameters : 1> client Socket. 2> receive content buffers . 3> receives the content buffer length . 4> receive mode . 0 indicates a blocking type . You must wait for the server to return data .      return value: If successful, returns the number of bytes received. failure is returned Socket_error           */     // 4. server receives messages     // Create receive content buffers . uint8_t buffer[]; // Accept message ssize_t len = recv (socketnumber, buffer, sizeof(buffer), 0);     NSLog (@ "len:%zd", Len); // Remove data from the accepted content buffer . NSData *data = [NSData datawithbytes:buffer Length:len]; //Convert binary stream data to string type. nsstring *receive = [[NSString alloc] Initwithdata:data encoding:nsutf8stringencoding]; NSLog (@ "receive:%@", receive);     // 5. Close Socket Close (socketnumber);

Socket Introduction (Master Socket family)