tcp echo

https://blog.csdn.net/fcx520/article/details/49889985

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
 
static const int MAXPENDING = 5;
 
static const int BUFSIZE = 1024;
 
void HandleTCPClient(int clntSocket);
 
void DieWithUserMessage(const char *msg, const char *detail);
 
void DieWithSystemMessage(const char *msg);
 
int main(int argc, char *argv[]) 
{
    if(argc != 2)
          DieWithUserMessage("Parameter(s)", "<Server Port>");
 
    in_port_t servPort = atoi(argv[1]);
 
    // Create socket for incoming connections
    int servSock;
    if((servSock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0 ) {
        DieWithSystemMessage("Socket() failed");
    }
 
    // Construct local address structure
    struct sockaddr_in servAddr;            // Local address
    memset(&servAddr, 0, sizeof(servAddr));        // Zero out structure
    servAddr.sin_family =  AF_INET;            // IPv4 address family
    servAddr.sin_addr.s_addr = htonl(INADDR_ANY);    // Any incoming interface.
    servAddr.sin_port = htons(servPort);
    
    //Bind to the local address
    if (bind(servSock, (struct sockaddr*) &servAddr, sizeof(servAddr)) < 0 )
        DieWithSystemMessage("bind() failed");
 
    // Mark the socket so it will listen for incoming connections
    if (listen(servSock, MAXPENDING) < 0 )
        DieWithSystemMessage("listen() failed");
 
    for (;;) {                    // Run forever
        struct sockaddr_in clntAddr;        // Client address
        // Set length of client address structure (in-out parameter)
        socklen_t clntAddrLen = sizeof(clntAddr);
        
        // Wait for a client to connect
        int clntSock = accept(servSock, (struct sockaddr*) &clntAddr, &clntAddrLen);
        if ( clntSock < 0 )
            DieWithSystemMessage("accept() failed");
        
        // clntSock is connected to a client!
        
        char clntName[INET_ADDRSTRLEN];        // String to contain client address
        if (inet_ntop(AF_INET, &clntAddr.sin_addr.s_addr, clntName, sizeof(clntName)) != NULL )
            printf("Handling client %s/%d\n", clntName, ntohs(clntAddr.sin_port));
        else
            puts("Unable to get client address");
 
        HandleTCPClient(clntSock);
        
    }
}
 
void HandleTCPClient(int clntSocket)
{
    char buffer[BUFSIZE];    // Buffer for echo string
    
    // Receive message from client.
    ssize_t numBytesRcvd = recv(clntSocket, buffer, BUFSIZE, 0);
    if ( numBytesRcvd < 0 )
        DieWithSystemMessage("recv() failed");
 
    // Send received string and receive again until end of stream.
    while ( numBytesRcvd > 0 ) {  //0 indicates end of stream.
        // Echo message back to client.
        ssize_t numBytesSent = send(clntSocket, buffer, numBytesRcvd, 0);
        if ( numBytesSent < 0 )
            DieWithSystemMessage("send() failed");
        else if ( numBytesSent != numBytesRcvd )
            DieWithUserMessage("send()", "send unexpected number of bytes");
        
        // See if there is more data to receive.
        numBytesRcvd = recv(clntSocket, buffer, BUFSIZE, 0);
        if ( numBytesRcvd < 0 )
            DieWithSystemMessage("recv() failed.");
    }
    
    close(clntSocket);     // Close client socket.
}
 
void DieWithUserMessage(const char *msg, const char *detail) 
{
    fputs(msg, stderr);
    fputs(": ", stderr);
    fputs(detail, stderr);
    fputc('\n', stderr);
    exit(1);
}
 
void DieWithSystemMessage(const char *msg) 
{
    perror(msg);
    exit(1);
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

void DieWithUserMessage(const char *msg, const char *detail) {
    fputs(msg, stderr);
    fputs(": ", stderr);
    fputs(detail, stderr);
    fputc('\n', stderr);
    exit(1);
}
 
void DieWithSystemMessage(const char *msg) {
    perror(msg);
    exit(1);
}

int main(int argc, char **argv){
 
    if ( argc < 3) {
        DieWithUserMessage("Parameter(s)", "<IP> <PORT> [<MESSAGE>]");
    }
 
    // Create local socket
    int sock;
    if ( ( sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP ) ) < 0 ) {
        DieWithSystemMessage("socket() failed.");
    } 
 
    int servPort = atoi(argv[2]);
 
    // Create server address
    struct sockaddr_in servAddr;
    memset( &servAddr, 0, sizeof(servAddr) );
    servAddr.sin_family = AF_INET;
    servAddr.sin_port = htons(servPort);
    inet_pton(AF_INET, argv[1], &servAddr.sin_addr.s_addr);
 
    // Connect to server
    if ( (connect( sock, (struct sockaddr *) &servAddr, sizeof(servAddr))) < 0  ) {
        DieWithSystemMessage("connect() failed.");
    }
 
    // Send Message to server
    ssize_t sentByteLen = send( sock, argv[3], sizeof(argv[3]), 0);
    if ( sentByteLen > 0 ) {
        printf("send: %s\tbytes:%d\n", argv[3], sentByteLen);
    } else {
        DieWithSystemMessage("send() failed");
    }
    
    // Receive Message from server
    char recvBuf[sentByteLen];
    ssize_t recvByteLen = recv( sock, recvBuf, sentByteLen, 0);
    if ( recvByteLen > 0 ) {
        printf("recv: %s\tbytes:%d\n", recvBuf, recvByteLen);
    } else {
        DieWithSystemMessage("recv() failed");
    }
 
    close(sock);
    
    printf("end!\n");
}