Socket-Based C/S network communication (medium) and iossocket in iOS

Socket-Based C/S network communication (medium) and iossocket in iOS

Based on the previous knowledge, next we will introduce Socket programming based on the TCP protocol. Because the Socket requires a client and a server, what is implemented now is a simple program about the server. The server uses the CFStream class for implementation.

This server uses the Command Line Tool in Xcode as the server; of course, you can also use the iPhone as the server, but to use other frameworks, such as AsyncSocket (https://github.com/roustem/AsyncSocket ), there are sockets implemented by UDP and TCP. There are also many operations on data streams in the source program, which can be used for in-depth understanding. Of course, it is also complicated.

Let's take a look at the simple TCP server program: (TCPServer. m)

<Pre name = "code" class = "objc"> # import <CoreFoundation/CoreFoundation. h> # include <sys/socket. h> # include <netinet/in. h> # define PORT 8734 void AcceptCallBack (CFSocketRef, CFSocketCallBackType, CFDataRef, const void *, void *); void Merge (CFWriteStreamRef stream, CFStreamEventType eventType, void *); void ReadStreamClientCallBack (CFReadStreamRef stream, CFStreamEventType eventType, voi D *); int main (int argc, const char * argv []) {/* defines a Server Socket reference */CFSocketRef sserver; /* Create socket context */CFSocketContext CTX = {0, NULL};/* create server socket TCP IPv4 set callback function */sserver = CFSocketCreate (NULL, PF_INET, SOCK_STREAM, IPPROTO_TCP, kCFSocketAcceptCallBack, (CFSocketCallBack) AcceptCallBack, & CTX); if (sserver = NULL) return-1; /* set whether to rebind the flag */int yes = 1; /* Set the socket property SOL_SOCKET to set tcp SO_REUSEADDR to rebind, yes to re-bind */setsockopt (CFSocketGetNative (sserver), SOL_SOCKET, SO_REUSEADDR, (void *) & yes, sizeof (yes);/* set the port and address */struct sockaddr_in addr; memset (& addr, 0, sizeof (addr )); // The memset function copies the specified address in memory. sin_len = sizeof (addr); addr. sin_family = AF_INET; // AF_INET is used to set IPv4 addr. sin_port = htons (PORT); // The value of the unsigned short integer in the htons function is converted to the "Network byte order" addr. sin_addr.s_add R = htonl (INADDR_ANY); // INADDR_ANY has kernel allocation, and the htonl function unsigned long integer number is converted to "Network byte order"/* copies from the specified byte buffer, an unchangeable CFData object */CFDataRef address = CFDataCreate (kCFAllocatorDefault, (UInt8 *) & addr, sizeof (addr);/* set Socket */if (CFSocketSetAddress (sserver, (CFDataRef) address )! = KCFSocketSuccess) {fprintf (stderr, "Socket binding failed \ n"); CFRelease (sserver); return-1 ;} /* Create a Run Loop Socket source */CFRunLoopSourceRef sourceRef = kernel (kCFAllocatorDefault, sserver, 0);/* Add the Socket source to the Run Loop */CFRunLoopAddSource (CFRunLoopGetCurrent (), sourceRef, kCFRunLoopCommonModes); CFRelease (sourceRef); printf ("Socket listening on port % d \ n", PORT);/* Run Loop */CFRunLoo PRun ();}/* after receiving the client request, the callback function */void AcceptCallBack (CFSocketRef socket, CFSocketCallBackType type, CFDataRef address, const void * data, void * info) {CFReadStreamRef readStream = NULL; CFWriteStreamRef writeStream = NULL;/* the meaning of the data parameter is: if the data type is bytes, the data is a pointer of the encoding type */CFSocketNativeHandle sock = *) data;/* Create a read/write Socket stream */CFStreamCreatePairWithSocke T (kCFAllocatorDefault, sock, & readStream, & writeStream); if (! ReadStream |! WriteStream) {close (sock); fprintf (stderr, "CFStreamCreatePairWithSocket () failed \ n"); return;} CFStreamClientContext streamCtxt = {0, NULL }; // register two callback functions: CFReadStreamSetClient (readStream, callback, ReadStreamClientCallBack, & streamCtxt); CFWriteStreamSetClient (writeStream, callback, WriteStreamClientCallBack, & streamCtxt); // Add CFReadS to the loop TreamScheduleWithRunLoop (readStream, CFRunLoopGetCurrent (), iterator); iterator (writeStream, CFRunLoopGetCurrent (), iterator); CFReadStreamOpen (readStream); CFWriteStreamOpen (writeStream );} /* call */void ReadStreamClientCallBack (CFReadStreamRef stream, CFStreamEventType eventType, void * clientCallBackInfo) {UInt8 buff [255]; CFReadStrea MRef inputStream = stream; if (NULL! = InputStream) {CFReadStreamRead (stream, buff, 255); printf ("received data: % s \ n", buff); CFReadStreamClose (inputStream); CFReadStreamUnscheduleFromRunLoop (inputStream, CFRunLoopGetCurrent (), callback); inputStream = NULL;}/* The write stream operation client calls */void WriteStreamClientCallBack (CFWriteStreamRef stream, CFStreamEventType eventType, void * clientCallBackInfo) when reading data) {CFWriteStreamRef outputStream = strea M; // output UInt8 buff [] = "Hello, client! "; // Information sent to the client if (NULL! = OutputStream) {CFWriteStreamWrite (outputStream, buff, strlen (const char *) buff) + 1); // close the output stream CFWriteStreamClose (outputStream); CFWriteStreamUnscheduleFromRunLoop (outputStream, CFRunLoopGetCurrent (), kCFRunLoopCommonModes); outputStream = NULL ;}}

This program only involves simple data flow operations. For detailed data flow operations, see the source code of AsyncSocket. So far, a server has been implemented.

To be continued ......

What Is A socket network? What is the C-S structure?

Socket is a reference to the Communication Connection of another network-based application. Applications usually send requests to or accept network requests through sockets. The socket is generally located at the Session Layer. The c/s structure is the client server mode. One or more large computers centrally manage and access shared databases, which are called servers. Processing of other applications is distributed to other computers on the network. B/s is a moderate server structure. Several computer workstations are connected to one or more file servers through communication links. For example, a cashier in a supermarket.

Use Socket to write a C/S structure program to enable the client to send "hello, the server receives, and the server returns" you are hospitable"

Below is the server side
Import java.net .*;
Import java. io .*;

Public class SocketTest {

Public static void main (String [] args) throws Exception {
// Boolean isquit = true;
InputStream is;
OutputStream OS;
Byte [] buf = new byte [20];
String str;
ServerSocket ss = new ServerSocket (8000 );
// While (isquit) can be listened continuously without comments
{
Socket s = ss. accept ();
Is = s. getInputStream ();
OS = s. getOutputStream ();
Is. read (buf );
Str = new String (buf );
System. out. println (str );
OS. write ("Hello, client! ". GetBytes ());
}

}
}
Below is the client
Import java.net .*;
Import java. io .*;

Public class Client {

Public Client (){
}

Public static void main (String [] args) throws Exception
{
OutputStream OS;
InputStream is;
Byte [] buf = new byte [20];
String str;

Socket s = new Socket ("127.0.0.1", 8000 );

OS = s. getOutputStream ();
Is = s. getInputStream ();

OS. write ("hello". getBytes ());
Is. read (buf );
Str = new String (buf );
System. out. println (str );
}

}
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