一、苏格拉底挑战

二、遇见的问题

三、实践和代码

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <unistd.h>
#define MAX 256
#define SERVER_HOST "localhost"
#define SERVER_IP "127.0.0.1"
#define SERVER_PORT 1234
struct sockaddr_in server_addr, client_addr;
int mysock, csock; // socket descriptors
int r, len, n; // help variables
int server_init()
{
printf("================== server init ======================\n");
// create a TCP socket by socket() syscall
printf("1 : create a TCP STREAM socket\n");
mysock = socket(AF_INET, SOCK_STREAM, 0);
if (mysock < 0){
printf("socket call failed\n"); exit(1);
}
printf("2 : fill server_addr with host IP and PORT# info\n");
// initialize the server_addr structure
server_addr.sin_family = AF_INET; // for TCP/IP
server_addr.sin_addr.s_addr = htonl(INADDR_ANY); // This HOST IP
server_addr.sin_port = htons(SERVER_PORT); // port number 1234
printf("3 : bind socket to server address\n");
r = bind(mysock,(struct sockaddr*)&server_addr,sizeof(server_addr));
if (r < 0){
printf("bind failed\n"); exit(3);
}
printf(" hostname = %s port = %d\n", SERVER_HOST, SERVER_PORT);
printf("4 : server is listening ....\n");
listen(mysock, 5); // queue length = 5
printf("=================== init done =======================\n");
}
int main()
{
char line[MAX];
server_init();
while(1){ // Try to accept a client request
printf("server: accepting new connection ....\n");
// Try to accept a client connection as descriptor newsock
len = sizeof(client_addr);
csock = accept(mysock, (struct sockaddr *)&client_addr, &len);
if (csock < 0){
printf("server: accept error\n"); exit(1);
}
printf("server: accepted a client connection from\n");
printf("-----------------------------------------------\n");
printf("Clinet: IP=%s port=%d\n",
inet_ntoa(client_addr.sin_addr),
ntohs(client_addr.sin_port));
printf("-----------------------------------------------\n");
// Processing loop: client_sock <== data ==> client
while(1){
n = read(csock, line, MAX);
if (n==0){
printf("server: client died, server loops\n");
close(csock);
break;
}
// show the line string
printf("server: read n=%d bytes; line=%s\n", n, line);
// echo line to client
n = write(csock, line, MAX);
printf("server: wrote n=%d bytes; ECHO=%s\n", n, line);
printf("server: ready for next request\n");
}



#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <unistd.h>
#define MAX 256
#define SERVER_HOST "localhost"
#define SERVER_PORT 1234
struct sockaddr_in server_addr;
int sock, r;
int client_init()
{
printf("======= clinet init ==========\n");
printf("1 : create a TCP socket\n");
sock = socket(AF_INET , SOCK_STREAM, 0);
if (sock<0){
printf("socket call failed\n"); exit(1);
}
printf("2 : fill server_addr with server's IP and PORT#\n");
server_addr.sin_family = AF_INET;
server_addr.sin_addr.s_addr = htonl(INADDR_ANY); // localhost
server_addr.sin_port = htons(SERVER_PORT); // server port number
printf("3 : connecting to server ....\n");
r = connect(sock,(struct sockaddr*)&server_addr, sizeof(server_addr));
if (r < 0){
printf("connect failed\n"); exit(3);
}
printf("4 : connected OK to\n");
printf("-------------------------------------------------------\n");
printf("Server hostname=%s PORT=%d\n", SERVER_HOST, SERVER_PORT);
printf("-------------------------------------------------------\n");
printf("========= init done ==========\n");
}
int main()
{
int n;
char line[MAX], ans[MAX];
client_init();
printf("******** processing loop *********\n");
while (1){
printf("input a line : ");
bzero(line, MAX); // zero out line[ ]
fgets(line, MAX, stdin); // get a line from stdin
line[strlen(line)-1] = 0; // kill \n at end
if (line[0]==0) // exit if NULL line
exit(0);
// Send line to server
n = write(sock, line, MAX );
printf("client: wrote n=%d bytes; line=%s\n", n, line);
// Read a line from sock and show it
n = read(sock, ans, MAX );
printf("client: read n=%d bytes; echo=%s\n", n, ans);
}
}

}
}