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Linux network programming how to use multiple processes to achieve server concurrent access, many novices are not very clear about this, in order to help you solve this problem, the following editor will explain in detail for you, people with this need can come to learn, I hope you can gain something.

A classic example of using a multi-process approach to achieve concurrent access to the server.

The program realizes the function:

1. The client reads a line of text from standard input and sends it to the server.

two。 After receiving the text from the client, the server returns it to the client as is.

3. The client receives the text from the server, outputs it to standard output, and then continues the above steps.

Server-side process: after establishing the listening socket, wait for the connection of the client, after receiving a connection, create a child process to communicate with the client, and the main process continues to wait for the connection of other clients. The code is as follows:

# include

# include

# include

# include

# include

# include

# include

# include

# include

# define SERV_PORT 1113

# define LISTENQ 32

# define MAXLINE 1024

/ * connection handler function * /

Void str_echo (int fd)

Int

Main (int argc, char * argv []) {

Int listenfd,connfd

Pid_t childpid

Socklen_t clilen

Struct sockaddr_in servaddr

Struct sockaddr_in cliaddr

If ((listenfd = socket (AF_INET, SOCK_STREAM,0)) =-1) {

Fprintf (stderr, "Socket error:%s\ n\ a", strerror (errno))

Exit (1)

}

/ * the server side is populated with sockaddr structure * /

Bzero (& servaddr, sizeof (servaddr))

Servaddr.sin_family = AF_INET

Servaddr.sin_addr.s_addr = htonl (INADDR_ANY)

Servaddr.sin_port = htons (SERV_PORT)

/ * bind listenfd descriptor * /

If (bind (listenfd, (struct sockaddr*) (& servaddr), sizeof (struct sockaddr)) =-1) {

Fprintf (stderr, "Bind error:%s\ n\ a", strerror (errno))

Exit (1)

}

/ * listen for listenfd descriptor * /

If (listen (listenfd,5) =-1) {

Fprintf (stderr, "Listen error:%s\ n\ a", strerror (errno))

Exit (1)

}

For (;;) {

Clilen = sizeof (cliaddr)

/ * the server blocks until the client establishes a connection * /

If ((connfd=accept (listenfd, (struct sockaddr*) (& cliaddr), & clilen)) =-1) {

Fprintf (stderr, "Accept error:%s\ n\ a", strerror (errno))

Exit (1)

}

/ / after a client has established a connection

If ((childpid = fork ()) = = 0) {/ * child process * /

Close (listenfd); / * turn off the listening socket * /

Str_echo (connfd); / * process the client's request * /

Exit (0)

}

Close (connfd); / * the parent process closes the connection socket and continues to wait for other connections to arrive * /

}

}

Void str_echo (int sockfd) {

Ssize_t n

Char buf [MAXLINE]

Again:

While ((n = read (sockfd, buf, MAXLINE)) > 0)

Write (sockfd, buf, n)

If (n < 0 & & errno = = EINTR) / / interrupted, reentrant

Goto again

Else if (n < 0) {/ / error

Fprintf (stderr, "read error:%s\ n\ a", strerror (errno))

Exit (1)

}

}

Client process: create a connection socket, actively initiate a connection request to the server, establish the connection, wait for the standard input, after the input is completed, send the input to the server, and then receive the content sent by the server. and output the received content to standard output. The code is as follows:

# include

# include

# include

# include

# include

# include

# include

# include

# include

# define SERV_PORT 1113

# define MAXLINE 1024

Void str_cli (FILE * fp, int sockfd)

Int

Main (int argc, char * * argv)

{

Int sockfd

Struct sockaddr_in servaddr

If (argc! = 2) {

Fprintf (stderr, "usage: tcpcli\ n\ a")

Exit (0)

}

If ((sockfd=socket (AF_INET,SOCK_STREAM,0) =-1) {

Fprintf (stderr, "Socket error:%s\ n\ a", strerror (errno))

Exit (1)

}

/ * the client program fills in the data of the server * /

Bzero (& servaddr,sizeof (servaddr))

Servaddr.sin_family=AF_INET

Servaddr.sin_port=htons (SERV_PORT)

If (inet_pton (AF_INET, argv [1], & servaddr.sin_addr)

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